National MP Maurice Williamson complained to police last year that they would not lay fraud charges, and on behalf of a mother who believed her son had been given "heavy-handed" treatment.
Police have released further correspondence between the MP for Pakuranga and police since 2008.
Williamson was forced to resign as a minister last month after it emerged he telephoned a police officer to discuss an ongoing case against a wealthy Chinese businessman and National Party donor.
Williamson said previously that when he called police about Donghua Liu in January he thought he made it "crystal clear" he was not trying to interfere with the investigation.
He had said that as an MP he regularly acted as an advocate for the public, and it was as an MP he called police about Liu.
Today police revealed further contact, including a memorandum sent by a police officer to Superintendent John Tims, the district commander for Counties Manukau.
It detailed another call made by Williamson in "late 2013" about an investigation being undertaken by the financial investigation team.
The memo said that Williamson had started the conversation explaining that he was not seeking to interfere with the investigation. The MP said he was passing on what a complainant had told him and "that he was unhappy that [name deleted] would probably not face charges".
The police officer who Williamson spoke to subsequently discussed the matter verbally with a colleague.
The colleague advised that the view at the time "was that police would be unable to reach the required level of evidential sufficiency to bring charges".
It is unclear whether the matter was taken further.
Williamson has not responded to requests for comment.
His Pakuranga electorate office said it had no way of contacting him.
The Prime Minister's office said John Key was not aware of the specific contact.
"The prime minister was not aware of any specific phone calls/contact with the police other than those relating to Donghua Liu, however Mr Williamson had told the prime minister, as he had said publicly, he contacted the police on other matters from time to time.
"As Mr Williamson is no longer part of the executive, we have no further comment."
Liu was not a constituent of Williamson.
However, some of the cases appear to be genuinely on behalf of regular constituents.
Williamson wrote to former commissioner Howard Broad in 2008 on behalf of the mother of a young constituent in his electorate.
While the details of the troubles the boy had got into were redacted from the letter, the mother had reported to Williamson that her son had experienced "a very heavy-handed approach to a not so serious situation," Williamson wrote.
"A simple warning by the police officer involved in a case such as has been presented to me would appear to have sufficed," Williamson said.
He would "appreciate" it if Broad would investigate, he added.
A year later in 2009, Williamson again wrote to Broad, on behalf of another constituent who had come to New Zealand hoping to join the police, but was now in a "catch-22" because of immigration rules.
"[Name deleted] has had a number of years of service ... and his CV ... shows that he would appear to make an excellent serving police officer," Williamson said.
He asked Broad to investigate whether anything could be done for him.
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