Attorney-General Christian Porter and fellow cabinet minister Alan Tudge have been accused of sexual indiscretions, in a sensational Four Corners expose the government first tried to head off and then to discredit before it went to air.

In the program, former prime minister Malcolm Turnbull recounted how in December 2017 he had told Porter, then social services minister, that “I had heard reports of him being out in public having had too much to drink in the company of young women”.

“He knew that I was considering appointing him attorney-general, which of course is the first law officer of the Crown, and has a seat on the national security committee, so the risk of compromise is very very real,” Turnbull told the program.

Turnbull, however, was apparently satisfied Porter had taken on board the warning and went on within a fortnight to promote him to the post.

Rachelle Miller, a Liberal staffer in 2010-18, told the program she had a consensual affair with Tudge when on his staff. They were both married.

Tudge had “put a lot of pressure” on her, asking her “to ‘war game’ the lines that I was going to give the journalists to try and kill the story” when rumours spread of their liaison.

She said when she walked into the mid-winter ball at parliament house in 2017 with Tudge, she felt like “I was being used as an ornament”.

Miller described an alleged incident in Canberra’s Public Bar near parliament house, where there were journalists and politicians, when she and Tudge saw Porter with “someone in the corner, and they were clearly very intimate”.

“They were cuddling, they were kissing. It was quite confronting given that we were in such a public place”.

The woman was a young staffer who was working for another cabinet minister, according to Four Corners.

Miller said Tudge had demanded a journalist delete a photograph taken of Porter.

Before the program aired Four Corners executive producer Sally Neighbour tweeted: “The political pressure applied to the ABC behind the scenes over this story has been extreme and unrelenting. All credit to the ABC’s leadership for withstanding it”.

The program, “Inside the Canberra Bubble” focused on what it described as the “heady, permissive culture” around federal politics that “can be toxic for women”. Its investigation questioned “the conduct of some of the most senior politicians in the nation”.

In Senate estimates the ABC’s managing director David Anderson faced hostile questioning from Liberal senators, with pre-emptive attacks on the program for not looking at the behaviour of members of other parties.

Anderson strongly defended the program’s integrity including saying the ABC chair Ita Buttrose had seen it and approved it going to air.

He said government staff had questioned whether the program was in the public interest, but had not made threats. The Prime Minister’s Office had not been involved.

The controversial investigation will intensify the criticisms of the ABC constantly made by some in the Coalition and media critics of the public broadcaster.

The program presented a damaging picture of Porter, delving back decades to expose his attitudes to and comments about women.

Barrister Kathleen Foley said she knew Porter from when she was 16. She was in the Western Australian state debating team and he was brought in to coach it; later she knew him when she was at the WA state solicitor office and he was at the office of the director of public prosecutions.

“I’ve known him to be someone who was in my opinion, and based on what I saw, deeply sexist and actually misogynist in his treatment of women, the in way that he spoke about women,” she said.

In a statement late Monday night Porter said many of the claims on Four Corners were defamatory and “I will be considering legal options.”

He “categorically rejected” the “depiction of interactions” at Public Bar.

“The other party subjected to these baseless claims directly rebutted the allegation to 4 Corners, yet the programme failed to report that. This fact usually would be expected to be included in a fair or balanced report.”

Porter said that journalist Louise Milligan “never contacted me or my office, despite my awareness that for many months she has been directly contacting friends, former colleagues, former students – even old school friends from the mid 1980’s - asking for rumours and negative comment about me.

"The ABC’s Managing Director told a Senate Committee just today that all relevant information had been provided to Ministers who were the subject of tonight’s programme – that is not the case,” Porter said.

He said that in his time as attorney-general in Turnbull’s government, “I never had any complaint or any suggestion of any problem from Malcolm regarding the conduct of my duties as AG until the last week of his Prime Ministership when we had a significant disagreement over the Peter Dutton citizenship issue”.

Porter did apologise for sexist material he contributed to a law students’ magazine some 24 years ago.

Tudge, who is now Minister for Population, Cities and Urban Infrastructure, said in a statement after the program: “Tonight, matters that occurred in my personal life in 2017 were aired on the ABC’s Four Corners program.

"I regret my actions immensely and the hurt it caused my family. I also regret the hurt that Ms Miller has experienced.”

The President of the Law Council, Pauline Wright, said: “Allegations of misconduct regarding public or elected officials require an appropriate framework for investigation, which is why the Law Council has long called for an integrity commission to be established at the federal level with appropriate powers and definitions of misconduct”.

Porter is in charge of the legislation recently released in draft form for an integrity commission.