Sydney: Australian Prime Minister Tony Abbott on Tuesday said he has lost confidence in the head of the nation’s Human Rights Commission, calling a report criticising the detention of asylum-seeker children a “political stitch-up”.

The government-funded commission, which released the study earlier this month, said its 10-month investigation of 11 detention centres found widespread sexual assault, self-harm and severe mental disorders among children locked up.

Abbott told parliament the inquiry should have been released when the previous Labor government was in power, as more children were held in detention at that time. His conservative government took office in September 2013.

“It’s absolutely crystal clear this inquiry by the president of the Human Rights Commission is a political stitch-up,” he said of commission president Gillian Triggs, a respected international lawyer.

“This government has lost confidence in the president of the Human Rights Commission.”

He added: “It’s too political to have an inquiry into children in detention when there is 1,400 of them but it’s not too political to do it when the number is under 200.”

Australia has long come under international pressure over the detention of asylum-seekers arriving by boat, particularly in offshore camps on the Indian Ocean territory of Christmas Island and on Nauru and Manus Island in the Pacific.

The numbers of children in immigration detention peaked at 1,992 in mid-2013 under the former Labor administration, but they have been significantly reduced to several hundred since the Abbott government was elected.

Abbott’s remarks came as Attorney-General George Brandis told a parliamentary hearing Triggs “fatally compromised” the organisation over the report’s timing.

“By catastrophic error of judgment, she placed the commission in a position where it could no longer command the confidence of both sides of politics, or indeed my own confidence as the minister, in her political impartiality,” Brandis said.

“So I had reached the conclusion, sadly, that Professor Triggs should consider her position.”

Triggs claimed in the hearing that the government sought her resignation two weeks before the “Forgotten Children” report was released, but she rejected the request.

The report criticised both sides of politics for their policies towards asylum-seeker children and recommended a national inquiry be established to examine mandatory detention.

Some 50 prominent Australians, including former Liberal prime minister Malcolm Fraser, voiced concern about the government’s response in a letter to Abbott last week.

The letter said not heeding the advice of human rights monitors “risk a dangerous slide into a national culture of discrimination and inequity and, ultimately, of societal disruption and moral decline”.