Rotorua MP Todd McClay has described claims made about him by National MP Jami-Lee Ross as "baseless" and says he stands beside Simon Bridges.
Ross has claimed McClay knew of the false electoral return Ross is accusing the National Party leader of.
But McClay has told the Rotorua Daily Post the claims are "baseless".
Ross made the allegation about McClay as part of his claims that Bridges had filed a false electoral return.
Ross said Bridges asked him to collect a $100,000 donation which was then split into smaller amounts to hide it.
Ross said he would complain to police about the handling of donations made to the party.
He said McClay knew of the donation and had witnessed the "misleading electoral return".
"I know Simon filed a false return because Todd McClay and I spotted that in January and suggested it needed to be tidied up."
Ross has quit the National Party, though he said he still believed in the party's values.
In a media stand up in Wellington today, Bridges said he had complied with electoral laws and done nothing wrong.
Bridges said Ross was "lying, leaking" and "lashing out" and has welcomed police investigating the rogue MP's claims about donations to National.
He rejected Ross calling him a "corrupt" politician who was not fit to be prime minister.
Todd McClay said he stood beside Bridges.
"These claims are baseless. I agree with Simon Bridges, Mr Ross should take this to the police and they should investigate them fully."
McClay said that he backed Bridges "100 per cent".
"This is not a matter of leadership, it's about one individual who has shown significant disloyalty to every caucus member."
McClay said the entire caucus was disappointed. "We've been working very hard over the past year. Again, this is about one person who has shown great disloyalty to caucus."
But he didn't believe Ross' actions had caused any damage to National.
Bay of Plenty MP Todd Muller said he was "extremely disappointed" in Ross' actions.
"We get elected to work for the interests of our community, their interests must guide our actions, not ego-driven ambition and subsequent anger if you don't get the job you want from the leader.
"I was pleased the caucus support the expulsion motion. I think Simon has handled a very complex and sensitive issue very well and he has the complete support from me and the National caucus."
Tauranga-based Labour list MP Jan Tinetti said she didn't want to comment on the National Party issues.