The incident at Sparrow Early Learning in Mandurah in August last year prompted action in the State Administrative Tribunal over breaches of education and care service laws.

A Department of Communities investigation found that four children aged four years and under left the service by climbing through a large gap in a perimeter fence, while unnoticed and unsupervised.

The three girls and a boy were found by members of the public and returned unharmed to the centre.

In a statement on Friday, the department said the fence was known to be regularly damaged by vandals.

The gap in the fence had been spotted on the morning of the incident but had been inadequately repaired by staff.

"Being approved to operate a childcare service in Western Australia carries significant responsibilities and obligations to ensure the safety and wellbeing of children enrolled at the childcare service," the department's Deputy Director General Catherine Stoddart said.

"Perimeter barriers should be checked regularly and repairs carried out so as to protect against any child being able to leave the safety of a centre's grounds.

"The supervision policies and procedures must be robust and include frequent headcounts and premises checks, especially for those children with known abilities such as climbing fences or tall outdoor or indoor structures, to ensure all children are accounted for."

Ms Stoddart said staff should be trained in the service policies and procedures and operators must have systems in place to ensure they are followed.

Australian Associated Press