Maurice Williamson called a senior police officer in Counties Manukau on a separate criminal case in which he "merely wished to pass on" that a complainant in a fraud case was "unhappy" that police were not going to lay charges.
On the day that Mr Williamson resigned from his ministerial posts, the Detective Inspector Dave Lynch wrote to Superintendent John Tims because of the publicity surrounding the MP and said that he had been contacted by the MP in late 2013.
The phone call from Mr Williamson in October or November 2013 was about a complex financial case where the complainant was advised that it was unlikely the police would lay criminal charges, said Mr Lynch, according to the memo released today under the Official Information Act.
"When Mr Williamson phoned me he reiterated at the start of the conversation that he was not seeking to interfere in any police investigation but merely wished to pass on what [redacted] had advised him that he was unhappy that [redacted] would probably not face charges."
Mr Lynch was unaware of the details of the case and spoke with a colleague who said "the matter was quite complex but his current view was that police would be unable to reach the required level of evidential sufficiency to bring charges."
There was no further contact from Mr Williamson, said Mr Lynch.
• Maurice Williamson 'crossed the line' - PM
When Mr Tims referred the memo to Police National Headquarters on May 1, he said he had not had any conversations or dealings with the MP for Pakuranga about the matter.
Mr Williamson has not returned phone messages from the Herald today.
William tried to contact police ahead of story breaking
Earlier today the Herald revealed Mr Williamson asked a senior police officer to call him soon after learning the Herald was about to break a story that would ultimately lead to his resignation as a Minister.
Mr Williamson resigned from his ministerial portfolios this month after it was revealed that he twice called Superintendent John Tims, the Counties Manukau district commander, in January about the prosecution of wealthy businessman Donghua Liu for domestic violence offences.
Prime Minister John Key said the MP for Pakuranga had "crossed the line", despite assuring him he did not intend to influence the prosecution.
A timeline of events released under the Official Information Act this morning shows that Mr Williamson's office was provided with a copy of the emails that police planned to release to the Herald, which had also been given to the Prime Minister's office under the 'no surprises' policy.
The note for the evening of April 29 states "Mr Williamson attempts to contact District Commander Tims".
A spokesman for Police National Headquarters said Mr Williamson sent a text message to Mr Tims asking him to call.
"Superintendent Tims did not call or respond to the text."
The emails released to the Herald on May 1 showed that Mr Williamson rang Mr Tims about the family violence allegations again Liu. Mr Tims referred the inquiry to his Auckland counterpart, Superintendent Mike Clement, on January 20.
A week later, Mr Williamson rang Mr Tims again, who again asked Auckland City to respond.
Mr Clement tasked Inspector Gary Davey to follow up the request and "determine how we respond to MP Williamson".
"He [Mr Williamson] started by saying that in no way was he looking to interfere with the process," Mr Davey reported back to his superiors.
"He just wanted to make sure somebody had reviewed the matter to ensure we were on solid ground as Mr Liu is investing a lot of money in New Zealand."
Mr Davey said he told Mr Williamson the criminal case was reviewed by the senior sergeant in charge of family violence cases, as well as the police prosecution team.
Watch: Maurice Williamson resigns
In the emails Mr Davey said he told the MP the police would carry on with the prosecution.
"I also explained the wider responsibility of police to pursue these matters [redacted]. I told Mr Williamson that the best advice he can give Mr Liu is to have him seek good legal advice. The conversation was polite and professional on both sides and he appeared to be accepting of the police position. I will leave the matter there unless I hear otherwise."
Liu has since pleaded guilty to male assaults female and assault with intent to injure and will reappear in the Auckland District Court next month.
After his resignation, Mr Williamson said he made five or six calls to police each year on behalf of people who approached him.
In Mr Liu's case he said: "There was no intention to do anything about screwing the outcome, but just to work out the focus of it.
"When I hung up I literally did not see that that was anything other than what a member of parliament would normally do on behalf of somebody who had asked.
"However it has become clear that the police believe that it does cross a line, the Prime Minister thinks that it was inappropriate for me to have made the call."
He said he was told of the December incident by a friend of Liu and was told by Liu's interpreter there was confusion over the incident.
"I said I would find out from the police what the status of all this is and has it come to an end."
Mr Williamson said he was not "friends" with Liu.
"It is pretty hard to have a friend that you cannot speak a word of their language and they of yours."
Mr Williamson also lobbied a ministerial colleague to grant citizenship to Liu against official advice and performed the ceremony himself in his electorate office.
He also lobbied another National minister to relax the criteria for rich immigrants under the investment rules, which Liu also wanted changed before he goes ahead with a proposed $70 million property development which has stalled for three years.