Immigration Minister Scott Morrison is expected to be interrogated about children being held in immigration detention when he fronts a human rights inquiry in Canberra today.

The inquiry was launched by the Human Rights Commission in February and the commission’s president Gillian Triggs has already held three public hearings in Sydney and Melbourne.

• EXPLAINED Detained children to be released
• Cambodia asylum deal imminent

The commission is investigating the impact of detention on the health, wellbeing and development of children.

It has already heard explosive allegations from a former director of mental health services at detention centre service provider International Health and Mental Services (IHMS).

Psychiatrist Peter Young claimed the Immigration Department tried to cover-up the scale of mental illness among child asylum seekers by asking for figures documenting the problems to be withdrawn.

Earlier this week Mr Morrison announced plans to move hundreds of children from detention centres and community detention onto bridging visas by the end of the year.

The changes would apply to children under 10 and their families on the Australian mainland.

But Labor has criticised the Coalition for refusing to extend the policy to children being held on Nauru and Christmas Island.

Greens immigration spokeswoman Sarah Hanson-Young says the timing of the Mr Morrison’s announcement ahead of today’s hearing is not a coincidence.

“He needs to explain why children are being made to suffer, why their childhoods are being destroyed and what actions he will take given the damning evidence that’s come out in the inquiry already,” she said.

The Government says there are 876 children in detention centres, a reduction of more than 500 since the last election.

Mr Morrison’s office says at the end of July there were 1,547 children in the community detention program.