Prime Minister John Key personally phoned Solicitor General David Collins to pass on his gratitude for work on the so-called teapot tape case, two days before the election.
The Solicitor General's office is meant to be kept strictly independent from all political influence.
However, an email obtained under the Official Information Act showed Collins wrote to an unnamed counsel saying: "The PM phoned this morning and asked me to pass on to you his personal thanks for your work on Ambrose. He was very complimentary notwithstanding my attempts to say you were just doing your jobs! Well done. D "
The email is dated November 24 and referred to Bradley Ambrose, a freelance photographer who left an electronic device on a table, inadvertently recording a conversation between Key and Act Party leader John Banks.
A separate Official Information Act request was sent to the Office of the Prime Minister seeking a record of all correspondence pertaining to Key's conversation at Urban Cafe and the subsequent inquiry and High Court case.
In his response, Key's chief of staff Wayne Eagleson did not mention Key's phone call to Collins but did provide transcripts of media interviews, and a copy of a press release.
Ambrose asked the High Court to rule the conversation was public but this was rejected and Crown Law wanted Ambrose to pay costs of almost $14,000. That order for costs was withdrawn this month.
The Crown Law Office's description of the Solicitor General stated his duty was to give independent advice. "That independence is of considerable constitutional importance. Such impartial advice can be seen to be given without political direction, even on politically contentious issues."
A spokeswoman for the Prime Minister responded with a short statement, confirming Key rang Collins after the outcome of the case was known. "It is not uncommon for the Prime Minister to personally thank people for their hard work."