New Zealand's next Governor-General is expected to be named this week but it almost certainly won't be a former politician or a former judge.

Prime Minister John Key told reporters at his post-Cabinet press conference that, as a general rule, he did not think former politicians should be governors-general.

"I know it has happened with Sir Keith Holyoake for instance but, as a general rule, that is not my preference."

The announcement would be made "sooner than you think -- possibly this week".


Sir Jerry Mateparae's five-year term is up on August 31.

As a former Chief of Defence Force, he was the first non-judge appointed since the MMP electoral system began in 1996.

He was preceded in order by Sir Anand Satyanand, Dame Silvia Cartwright and Sir Michael Hardie Boys.

It was seen as great advantage to have a legal background because of the potentially greater role a Governor-General could play under the coalition building and minority governments associated with MMP politics.

Asked if the position needed someone with a legal background or just someone who could take advice, Mr Key said: "In the end I think you need someone who can carry out the duties and responsibilities of the Governor-General with the mana and respect that that office deserves.

"Clearly the person would have to be bright enough to understand themselves but also be able to take advice in the highly rare event that there was a significant constitutional issue or to make sure they discharge their responsibilities when it comes to the election process.

"Anybody that made the short-list in my mind of being able to be the Governor-General would be able to have the intellectual where-with-all to do that."