Prime Minister Scott Morrison has defended not immediately launching an inquiry into the conduct of federal minister Alan Tudge when revelations of an affair with a staffer were first revealed.

While the consensual affair was brought to light last year, Mr Morrison said the investigation was sparked by allegations of abuse, aired on Thursday, by Mr Tudge’s former lover Rachelle Miller.

Ms Miller alleged she was emotionally and physically abused during the 2017 affair, accusations Mr Tudge has denied.

The Liberal MP has agreed to stand aside as education minister while the investigation into the allegations proceed.

Mr Morrison said the matter was not formally investigated last year due to both parties indicating at the time it was a consensual relationship.

“At the time [last year], there was none of the suggestions that were made yesterday,” Mr Morrison said on Friday.

“These new matters have been raised in the statement, which I read carefully yesterday, and so that’s why I have asked my department to provide me with advice on potential implications for the ministerial standards.”

Former public servant Vivienne Thom will head the investigation.

Ms Miller said she would cooperate fully with the departmental investigation, but cast doubt on whether it would be truly independent or fair.

Mr Morrison said the investigation would be “fair and reasonable”, with there being more support mechanisms in place, following a year where the treatment of women in parliament has been highlighted.

“The reach-out [to Ms Miller] was given yesterday through the body that we set up at the same time when we set up the independent complaints mechanism and there’s also the counselling support,” he said.

“I understand yesterday that organisation reached out. That’s my understanding, that’s what I asked to be done.”

Ms Miller alleges Mr Tudge repeatedly chastised, bullied and belittled her.

She also accuses Mr Tudge of once physically kicking her from his hotel room bed until she ended up on the floor.

Mr Tudge has taken leave and said there was written evidence to contradict Ms Miller’s version of events.

As sights set towards next year’s federal election, Mr Morrison has said he is determined to see the Coalition stand women as candidates across the country.

While the NSW Liberal division has committed to gender parity for candidates at the 2022 poll, Mr Morrison said quotas in other jurisdictions were matters for state divisions.

It comes amid growing speculation about who will be preselected for the Liberals in the Victorian seat of Flinders, replacing outgoing Health Minister Greg Hunt.

Mr Hunt said he wanted to see a woman run for the Liberals in his electorate on the Mornington peninsula.

NBN director Zoe McKenzie is widely tipped to run for the seat.

“I want to see great female candidates running for us in seats right around the country, and I’m very determined to achieve that,” Mr Morrison said.

-AAP