Simon Bridges has "absolutely" abided by electoral donation rules, says a former general manager of the National Party.
Mr Bridges was accused of breaking the law by now-former National MP Jami-Lee Ross, in an explosive press conference on Tuesday.
Mr Ross has since released recordings and text messages he says shows Mr Bridges is "corrupt", but which haven't contained any smoking guns - and may have proved the party was following the law, according to one legal expert.
He has given the police his evidence, which may contain recordings he hasn't yet released.
Former party general manager Chris Simpson told Newshub Nation on Saturday he has no doubt Mr Bridges will be cleared of any wrongdoing.
"Simon Bridges used to be on the rules committee, and is a lawyer. And everything is also governed by the Electoral Act of 1983. And the Electoral Act is so detailed about what you can and can't do. I used to have it sitting on my table because I didn't want to go to jail."
He says the texts Mr Ross released show the party's current general manager Greg Hamilton was doing the right thing.
"If you look at those texts in detail, the general manager is trying to get the name of the donors. That's absolutely appropriate. If they hadn't done that, then absolutely - it would have been a legal issue."
According to Mr Ross, the donation at the centre of the allegations was $100,000 and came from a Chinese businessman. The party says the money came from eight different individuals. A recording of Mr Bridges and Mr Ross discussing the money featured talk of getting a Chinese candidate on the party list.
It's raised questions over whether wealthy foreigners have influence over New Zealand political parties. Mr Simpson says they have "absolutely nil" influence on National Party policy, and is just needed to pay the bills like any other "business".
"I used to call the politicians the salespeople, the retail arm - their job was to go out and sell… regarding policy, the way that you do policy is you put your head down and write policy."
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The Greens have called for stricter rules on donations, and suggested public funding as a way of getting rid of it altogether.
Mr Ross didn't answer requests to come on the show and give his side of the story. Mr Bridges declined.