New Zealand’s opposition leader has been secretly recorded calling one of his own MPs “f***ing useless” and making other questionable remarks as turmoil escalates within the conservative National Party.

Simon Bridges said he has apologised to MP Maureen Pugh for making the inappropriate comment.

Mr Bridges said he has no intention of resigning after a former colleague accused him of corruption, initiated a police investigation into him and posted the embarrassing phone conversation on Facebook.

Jami-Lee Ross
Former MP Jami-Lee Ross (AP)

MP Jami-Lee Ross resigned on Tuesday after saying Mr Bridges was corrupt because he hid a donation from a wealthy Chinese businessman by arranging for it to be split into smaller amounts in order to avoid it being publicly disclosed.

Mr Bridges denies the charge.

Mr Ross went to the police with what he claimed was evidence before posting the conversation with Mr Bridges.

During the conversation, Mr Ross tells Mr Bridges that two men, including Zhang Yikun, have donated 100,000 New Zealand dollars (£50,000) and had expressed interest in having another Chinese MP.

“Two Chinese would be nice, but would it be one Chinese and one Filipino, or what do we do?” Mr Bridges asks on the tape.

Simon Bridges
Mr Bridges accepted he had spoken bluntly (AP)

He talks about a possible “mercenary cull” and how he would like two or three MPs to leave, including Ms Pugh.

Mr Bridges said that while he might have been blunt, he was simply trying to reflect the growing diversity in the community.

“I’m not perfect, as that conversation shows. Perhaps I’m something of a rough diamond sometimes,” Mr Bridges said.

“But I sleep well at night because I’ve got my integrity.”

He said Mr Ross had been trying to set him up and may have been secretly recording him for months.

“He’s a terrible person,” Mr Bridges said.

Mr Ross said he believed Mr Bridges had broken electoral laws and he had handed over evidence to police investigators. He said he recorded the conversation because he was uncomfortable about the donations.

In a statement, police said they had received a complaint and would provide any relevant updates in a timely manner.

The National Party held power for nine years before being ousted last year by a liberal coalition led by Prime Minister Jacinda Ardern.