Police say the contact between a senior police officer and Botany MP Jami-Lee Ross is "entirely appropriate" - but will not corroborate Ross' claim that he is not the National Party leaker.

In a dramatic press conference this morning, Ross lashed out at National Party leader Simon Bridges, calling him corrupt, dishonest, and unfit to be prime minister. Bridges struck back, calling Ross a liar and a leaker.

Ross continued to insist he did not leak details of Bridges' travel expenses, despite the findings of a PwC report that found evidence pointing to Ross as the culprit. The findings, however, were inconclusive.

The report was independently assessed by John Billington, QC, who said Ross was the leaker on the balance of probabilities.

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Trawling through communications data from National MPs, the PwC report noted Ross communicated with Speaker Trevor Mallard, a Radio NZ reporter, and a senior police officer on several occasions, and on key dates of the leak saga.

This included talking on the phone with Counties Manukau East area commander Wendy Spiller hours before police told Bridges they had identified the sender of a text message about the mental health of the leaker.

Ross also called Spiller six times on two days, including on the day of a Radio NZ story about the text message. He had not called Spiller for at least seven months before the expenses saga, the PwC report said.

Ross today defended the phone calls, saying he was sharing "sensitive" information he had received about a police officer with the area commander of his electorate.

"I have a good relationship with my local police officer. Her name is Wendy Spiller. I heard information. I discussed that information with the local police inspector.

"Local MPs talking to local police officers is very common."

But he would not sign a privacy waiver so police could confirm his claim he was not the leaker.

"What the police do is up to them, but I'm not expecting the police to enter the political arena."

When contacted by the Herald, Spiller declined to comment and referred questions to the police media team.

A police spokesperson said: "Police are aware of the reason for a number of contacts with a police officer as highlighted in the PwC report. While we will not discuss the nature of these contacts for privacy reasons, we can say that they were entirely appropriate."

Ross said he would lay a formal complaint with police today over Bridges' handling of electoral donations, along with a recorded phone conversation and photographs that he released on Twitter today.

Bridges said he welcomed a police probe because it would clear him of any wrongdoing.

Police said they were aware of Ross' claims.

"Any information received by police will be assessed to determine what further steps may be required from a police perspective."