Dr Ting, a senior tax lecturer at the University of Sydney Business School, had spent years trying to unravel the complex tax avoidance strategies of multinationals.

"All this information suddenly came out," he recalls.

By forcing Apple to release and explain its global accounts, the hearings exposed for the first time the tactics that allows the tech giant – and other corporations – to successfully avoid paying tax on billions of dollars earned every year in the world's biggest economies.

It also added steam to a global crusade against rich companies shifting profits overseas, avoiding the hands of tax authorities and depriving cash-strapped governments of much-needed revenue.

Australia is now facing calls for a parliamentary inquiry into profit-shifting of its own, with the opposition, Ting and advocacy groups saying it could help expose the tax minimisation tactics of companies operating here.

The calls come as Australia gears up to host the high-powered G20 finance ministers meeting, kicking off on September 18 in Cairns, where its efforts to tackle tax avoidance strategies will come under international scrutiny. That meeting is a precursor to the all-important G20 Leaders Summit in Brisbane in November.

Part of the G20's agenda is to modernise the international tax system to keep pace with the way companies now do business.

Prime Minister Tony Abbott has pledged to have a "frank" discussion about the impact of digitalisation on tax revenues at the meetings in November. In January, at the World Economic Forum in Davos, he noted that "different national tax arrangements have not always kept up with the rise of services and the pervasiveness of digital technologies" .

So, the G20 will continue to tackle businesses artificially generating profits to chase tax opportunities rather than market ones," he said.

The government stepped up its rhetoric on Thursday this week, with Treasurer Joe Hockey warning that the government would not stand "idly by" while multinationals avoided tax.

Hockey revealed he had asked Tax Office commissioner Chris Jordan to "double his efforts" and undertake more extensive inquiries and audits of multinational companies.

"As the Prime Minister and I have both previously said, you should pay tax in the country where you've earned a profit. That's not just an essential tax principle, it is rational and fair," Hockey said.

There is stark evidence that Australia's corporate tax base is being eroded, with the burden of revenue falling increasingly heavily on individuals.

The proportion of income tax collected from business in Australia has shrunk over the past five years, falling from 23 per cent in 2007-08 to 19 per cent in 2012-13, according to the Australian Bureau of Statistics.

At the same time, the proportion of income tax collected from individuals rose from 37 per cent to 39 per cent.

Mr Jordan has estimated the government is losing up to $1 billion a year because of the tax minimising strategies of multinationals. Most of that is being lost, he says, due to weaknesses in the present tax system – and its failure to adapt to modern, globalised businesses with flexible arrangements.

The list of companies being exposed for their use of "flexible" cross-border strategies is long and ever-growing.

Airbnb is the latest company to admit that every dollar spent on its website in Australia is booked through an Irish subsidiary, despite the company's new chief executive, Sam McDonagh, revealing that Australians were among the most prolific users of the popular apartment-sharing website.

"We do everything we can to comply with all the taxation requirements in Australia," Mr McDonagh  said in an interview last week.

Google has pointed to the $15 million it pays in payroll and other taxes in Australia as part of its investment in the local workforce.

Similarly, an Airbnb spokeswoman says it contributed "$214 million in economic activity in one year in Sydney" by filling local suburbs with overseas tourists.

Fairfax Media has revealed that Swedish furniture chain IKEA paid just $8.3 million in local tax expenses last year on an operating profit of $92 million.

Most multinational tech companies operating in Australia are able to reduce their local tax bills substantially by billing through subsidiaries in low-tax jurisdictions, such as Singapore or Ireland.

This cat-and-mouse game is kept alive by the determination of low-taxing nations to remain competitive.

Ireland says its 12.5 per cent corporate tax rate helps it attract leading companies to set up on its shores and employ local people.

On a recent trade mission to Australia, its jobs minister, Richard Bruton, said the affairs of multinationals was "not an Irish issue". "We believe that it is perfectly legitimate to have a low corporate tax rate," he said.

Apple and Google have stolen the most headlines for these tactics. After deductions, the latter paid just $460,000 in tax expenses in Australia in the past financial year despite doubling its local profit to $46.5 million. And the practices are not confined to the tech industry.

"This is not just about Google hiding within the digital ether, but agribusiness and mining corporations too," says Oxfam Australia chief executive Helen Szoke.

"They employ similar accounting tactics and avoid paying their fair share, and this is devastating to developing country budgets."

Tax Office deputy commissioner Mark Konza has told the Committee for Economic Development of Australia that the agency is ramping up its focus on companies with "footloose", or mobile, assets.

Part of this crackdown involved audits of high-tech companies that were suspected of breaching the law.

On Thursday, Jordan said the agency was looking specifically at the tech sector to examine whether companies were correctly reporting their income. "I appreciate the Treasurer's encouragement to do more in this area and his statement reinforces the importance of our current work program," he said in a statement.

But while governments – including Australia's – are talking tough, some have doubts about the capacity or willingness of leaders to act on profit shifting and tax avoidance at this year's G20 Leaders Summit in Brisbane.

Observers say the federal government's record so far in tackling profit shifting has been mixed.

Even as Hockey, in his speech on Thursday, revealed he had asked the tax commissioner to "double his efforts", he is simultaneously cutting the Tax Office's staff by 10 per cent over the next 12 years. The agency lost 900 staff last year.

Hockey's speech on Thursday outlined the government's work to plug some of the loopholes being exploited by companies. But much of the work involves measures already announced, including changes to thin capitalisation rules that came into effect in July.

These rules are designed to prevent multinationals from profit shifting by allocating a disproportionate amount of debt in their Australian operations, claiming debt deductions in Australia and thereby reducing their Australian taxable income.

The changes, which reduce the "safe harbour" debt limit from 75 per cent to 60 per cent, were derived in part from Labor's $4 billion multinational tax package, announced before it lost government.

Labor says about $1 billion worth of these measures are yet to be implemented.

The Tax Office is also ramping up its involvement in automatic exchange of information with tax authorities overseas. This involves sending financial information to international regulators in a bid to catch wealthy tax cheats.

But the opposition says cuts to the Tax Office undermined efforts and leave it "woefully underpowered" in the fight against big firms.

Labor's assistant treasurer and former economics professor Andrew Leigh says the government's failure to implement the rest of Labor's reforms will mean multinationals will still be able to avoid more in tax than is being saved by many of the budget's welfare tightening measures.

These reforms relate to delays in reforming Australia's offshore banking regime, third-party compliance reporting and discrepancies between the tax footing of multinational corporations and domestic companies.

According to budget papers, they would amount to savings of $1.13 billion.

Dr Leigh accuses  the government of letting multinationals off the hook at a time when it is asking low-income earners to make significant sacrifices as part of its tough budget. "It flies in the face of the Treasurer's rhetoric around the age of entitlement needing to end, and all of us needing to do the heavy lifting," he says.

And Ting points to the government's hesitation to stand by tougher transparency measures introduced under Labor, which will force the top 200 companies in Australia to publish the amount of tax they pay starting from July next year.

While Finance Minister Mathias Cormann has said he would retain these laws, tax experts said a repeal has been considered.

As well as clamping down on thin capitalisation schemes, the government says it is closing another loophole known as hybrid mismatch arrangements, which allow companies to flout tax by exploiting the differences in the treatment of entities or transfers between two or more countries.

"This is a flaw that's been in our laws for more than a decade," Hockey said on Thursday.

The government said Labor's other measures announced before the election had not considered the full impact of changes on Australian business, particularly rules preventing companies from claiming interest deductions on investments overseas.

"Soon after the election the government was told that this measure would impose extra costs on Australian businesses seeking to expand offshore, and those already operating offshore, by denying legitimate business deductions for interest costs on their borrowings," Hockey said.

"Increasing taxes on Australian businesses seeking to expand into new markets is poor public policy."

Meanwhile, not surprisingly, big business has shown ambivalence towards global efforts to tackle corporate tax dodging.

A survey of 3000 companies in 40 different countries by law firm Grant Thornton showed only 19 per cent believed the OECD's action plan on base erosion and profit shifting would be successful.

And John-Henry Eversgerd, a partner at McGrathNicol who specialises in transfer pricing, warns that changes to the thin capitalisation rules could very well have the unintended effect of closing one loophole and opening others.

"It may result in more multinationals availing themselves of other tax minimisation options, such as including the value of intangible assets in their thin cap calculations, potentially even if those assets are not presently allowed to be recognised for accounting purposes," he says.

"This allowance is not well known but is growing in popularity and may result in significantly greater interest deductions."

But Ting says greater transparency and information sharing can have as much of an impact as changes to the law.

He points to the example of a Reuters investigation into Starbucks in Britain that lead to hearings into the company's tax affairs by the powerful Public Accounts Committee.

Likewise, the US congressional hearings followed a detailed expose of Apple's tax minimising strategies in the pages of The New York Times.

Ting is calling for an Australian parliamentary inquiry into the profit-shifting practices of multinationals, in the hope that it could prove as revelatory as those in Britain and the US.

"The last thing that practitioners would like to have is full transparency," he says. "The more information the public has, and the ATO has, the better it is for the government."

Changes to the law could give the Tax Office more powers to investigate, he says.

But the government has so far shied away from moves to introduce country-by-country reporting, which tax experts say is crucial in lifting the lid on where companies are hiding money offshore. Country-by-country reporting would force companies to publish a breakdown of their operations in each country in which they operate, including employee numbers, assets, sales, profits, and taxes, due and paid.

The government has also been criticised by Transparency International, a global anti-corruption group, for consulting with business before committing to a deal on the automatic exchange of information between it and other jurisdictions around the world.

On Thursday, the Treasurer said the Cairns meeting would review governments' progress on country-by-country reporting, as well as other harmful tax practices.

It also firmly committed to a common reporting standard for automatic exchange of information.

Mark Zirnsak, a director of the Justice and International Mission of the Uniting Church Synod of Victoria and Tasmania and a representative of the Tax Justice Network, welcomed the commitment and encouraged the government to consider further measures to address profit shifting, including introducing a public registry of the ultimate owners of companies and trusts, and introducing legislation to protect and reward whistleblowers who expose corporate tax evasion and tax avoidance.

"This has been very significant in breaking through the tax evasion operations that were run by Swiss banks for US citizens," he says.

Oxfam's Szoke says the G20 should be actively promoting worldwide tax transparency by requiring multinational corporations to make country-by-country reports publicly available.

"This would have a deterrent effect and also assist with tackling tax avoidance in developing countries where tax authorities have limited capacity," she said.

Meanwhile, advocacy group ActionAid urged the government to consider the impact of tax dodging on developing countries – not just Australian taxpayers.

"If this government is serious about protecting the interests of developing countries, they must lead further reform," its Australian executive director Archie Law said.

Ting says it is a good time for Australia to consider whether it is worth having a US-style inquiry to grill multinationals about their operations here.

"If we had that committee, we could find out, for example with Apple, exactly what transactions Apple Australia has had with other related parties and all their financial statements," he says.