MP Jami-Lee Ross said he would resign on Friday but has yet to do so.

Rogue MP Jami-Lee Ross will not quit Parliament and has admitted to an affair with a fellow married MP.

Ross had earlier said he would resign on Friday, and then contest a by-election in his seat of Botany as an independent.

But in an interview with Newstalk ZB and later on Twitter on Friday evening he pledged to stay on in Parliament to continue his war against National leader Simon Bridges, saying the party had "changed the rules" by lifting the bedsheets on him so much that he wouldn't be able to fight a by-election in Botany.

"I have not submitted a resignation letter to the Speaker. I intended to do that today. I will instead stay on as an MP to continue speaking out about the internal operations of the National Party," Ross tweeted.

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In the Newstalk ZB interview Ross suggested the National Party might be responsible for a Newsroom story released on Thursday about four women who said they either been bullied by him or had consensual but threatening sexual relationships with him. Ross accepted that he had affairs with some women but disputed aspects of the story.

Newsroom co-editor Tim Murphy laughed off Ross' allegation.

"We started this inquiry a long time ago with every likelihood it would have been highly uncomfortable for the National Party and its MP. The fact he has divorced from them did not affect our inquiries at all."

Ross said as the party had changed the rules, he was too.

In a statement late on Friday, National said it was considering its options.

"What Jami-Lee has done and continues to do is unacceptable and the more that comes to light the more we know we made the right decision to expel him from the Caucus," it said.

"We are supporting those women who came to us as a result of Jami-Lee's behaviour."

Parliamentary privilege would mean anything Ross said in the House would not be covered by defamation laws.

Since the National Party caucus has expelled him, Ross would automatically be recognised as an independent MP by the Speaker.

If he did officially tell Speaker Trevor Mallard he was an independent, the new "waka jumping" law would mean he would have to leave Parliament. That would need to happen if Ross was to seek new parliamentary funding as the leader of his own party.

National has notified the Speaker under Standing Orders that Ross is no longer a member of the party and it could still use the "waka jumping" law to kick him out of Parliament. That would involve writing a specific letter to the Speaker.

National shadow leader of the house Gerry Brownlee said the party would assess its options.

"We're just quite frankly a bit over spending any time on this guy's concerns," Brownlee said.

He said it wasn't surprising that Ross had opted not to resign, as he would have "taken soundings in his electorate and knew that his prospects of being an independent member were minimal."

Mallard said the news would mean there was no change from the current position, where Ross is recognised as an independent MP.

Legal expert Graeme Edgeler said for the National Party to use the waka jumping law, it would have to prove that Ross was in some way subverting the proportionality of Parliament.

ROSS ADMITS AFFAIRS

Also on Newstalk ZB, Ross admitted to an affair with a married MP and a separate one with a former staffer.

He apologised to his wife and any other women he had hurt.

"I owe my wife a huge apology. I have done some things that I am not proud of. I have apologised to her in person and I am going to continue to apologise to her," Ross told Newstalk ZB.

"The bottom line is I haven't been a good husband."

Ross still disputed parts of the allegations, reported on by Newsroom, and named the married MP he had an affair with.

But Newstalk ZB chose not to name the woman.

NEW TAPE SURFACES

Newstalk ZB played a portion of a new recorded conversation on Friday afternoon ahead of a planned interview with Ross.

The tape was mentioned earlier this week and contains a conversation between Ross and Bridges on allegations about Ross' behaviour with women.

The tape is hard to make out, but Newstalk ZB believed it contained Bridges responding to Ross' request for natural justice by saying: "Honestly Jami-Lee if I gave you natural justice on these issues it wouldn't be four or five, it would be 15."

Ross discussed this conversation several days ago, but he characterised it as a "threat" from Bridges.

National deputy leader Paula Bennett has said the allegations were not about harassment as Ross claimed but concerned "inappropriate behaviour for a married MP".

Ross has denied any allegations of harassment - including the ones contained in a Newsroom story that featured four women complaining of abusing behaviour, with two complaining of an unhealthy but consensual sexual relationship.

Ross said he was considering his legal options on the Newsroom story.

Earlier on Friday two National MPs told Stuff they had been approached by Ross with leading questions and now believe he had taped those conversations.

NZ First leader Winston Peters won the waka jumping law in coalition negotiations. When asked if this case proved why the law was needed, Peters said "you guys are finally on to it."