Gillian Triggs has unloaded on the Turnbull government, labelling its actions "disgraceful", and accusing it of abusing executive power and manipulating the truth.

In her first public speech since stepping down as president of the Australian Human Rights Commission in July, Professor Triggs attacked Coalition government ministers for interfering with the judicial system and for destroying the integrity of Parliament by peddling "alternative facts".

"A culture of post-truth has allowed politicians and Parliament to reject evidence based reports by credible agencies in favour of populist decision-making that denies the truth and responds to fear," she told UNSW's Power to Persuade symposium in Canberra on Wednesday.

"This is particularly the case in relation to refugees, asylum seekers, terrorism, and conflict matters in general," she said.