National MP Jami-Lee Ross is to resign his seat and step down from the National Party, and will stand as an independent in any by-election for his Botany seat.

Speaking to media at Parliament in a stand-up that lasted almost an hour, he alleged Mr Bridges had broken electoral donation law and said he would put in an official police complaint.

Watch Jami-Lee Ross speaking to media at Parliament:

Mr Ross said he had had a mental breakdown as pressure was ramped up on him to leave the party.

Mr Ross was speaking as MPs met in caucus to decide whether to suspend him after leader National leader Simon Bridges yesterday identified Mr Ross as the likely leaker of his travel expenses. Minutes before this was revealed, Mr Ross went on Twitter with a range of allegations against the leader.

Mr Ross said today it was clear he'd had a falling out with with leader Simon Bridges.

He said he once thought Mr Bridges was capable of being Prime Minster, "but now that I see what he's really like it is clear that he's not".

"Simon is a flawed individual without a moral compass."

Mr Ross said Mr Bridges breached electoral law several times, and that it was not acceptable.

"I believe Simon Bridges is a corrupt politician," he said.

He alleged Mr Bridges had carried out unlawful activity relating to election donations, including activity which Mr Bridges denied yesterday.

"Certainly I reject any allegation of the sort in terms of unlawful activity, it's simply not true," Mr Bridges told media yesterday.

Mr Ross claimed that Mr Bridges asked him to collect a $100,000 donation from a wealthy businessman and was at pains to point out the donation should not be made public. He said the donation was split into smaller amounts below the $15,000 declaration threshold.

He said he would release photos to prove the meeting between the businessman and Mr Bridges took place.

Mr Ross said his dramatic falling-out with Mr Bridges was the reason he was the target of a campaign to push him out of the party.

The campaign started three weeks ago, he said.

He was "marched to Simon Bridges' office" where he was told four women had approached deputy leader Paula Bennett, claiming Mr Ross had harassed them. He said Mr Bridges asked him to resign his portfolios, leave Parliament, and return to the backbench at the beginning of next year.

He strenously denied allegations he had harrassed anyone.

Mr Ross said was deeply hurt that Mr Bridges characterised his health problems as embarrassing.

He said his mental health was better now, and a doctor had told him he was fit to make his own decisions about his career.

Mr Ross said he did not leak Mr Bridges' expenses, but he leaked the text message from the person who did, which said the person who had leaked the information was in a fragile mental state, and asking for the inquiry into the leak to be called off.

He said the Botany by-election would be a referendum on Mr Bridges' leadership.