Corrective Services Minister Murray Cowper has admitted "fundamental failures" by State Government agencies led to the murder of domestic violence victim Andrea Pickett in January 2009.
Mrs Pickett's estranged husband Kenneth Charles Pickett stabbed her 17 times after repeatedly breaching violence restraining orders.
He was also jailed previously for threatening to kill her.
In an interview with the ABC's Four Corners program to be aired tonight, Mr Cowper criticised a November 2008 decision by the Prisoners Review Board to release Pickett just weeks after telling it he remained a threat to his wife.
"Mysteriously and unexplainably … he was released on parole," Mr Cowper said.
"That was a deadly mistake in my view."
Pickett is serving life in jail for murdering his wife of 23 years in front of one of their 13 children.
The death of Mrs Pickett, 39, who repeatedly reported VRO breaches and sought police protection and crisis care accommodation to escape her husband, was the subject of a coronial inquest last month.
Coroner Alastair Hope criticised WA Police, the Department of Corrective Services and Department for Child Protection and found there was no plan in place to protect Mrs Pickett.
Mr Cowper also criticised the police response to Pickett threatening Mrs Pickett with a knife on Reid Highway, Mirrabooka and later trying to break into the house where she was staying while armed with a 20cm knife.
Pickett was declared armed and dangerous but police did not organise a search of the area.
"I agree that there should have been a proper investigation in relation to that matter," Mr Cowper, a former police officer, said.
He said that under stronger domestic violence laws the Government had introduced, two breaches of a VRO would result in arrest and a third would attract a jail term.
"The Government hasn't been sitting back idly waiting for a coroner's report to come down and clearly state that there have been some fundamental failures on behalf of a number of Government departments in respect to this," he said.
"As a father, as a husband and as a former police officer, I'm very sorry in relation to what happened to Mrs Pickett and her extended family."