Northland MP John Carter is heading for the Cook Islands to become a diplomat - a job he has been "training" for since 1975 when he first visited the islands on a rugby trip.

Mr Carter said yesterday that trip - before he became an MP - and subsequent holidays set him up with ongoing connections with several Cook Islands politicians.

Foreign Affairs Minister Murray McCully announced last week that Mr Carter would become the new High Commissioner to the Cooks - an appointment tipped by the Herald in November.

Mr Carter, who arrived in Parliament in 1987, will leave in July for the Cook Islands. A byelection will not be required for his Northland electorate because he will leave it within six months of the November 26 election.

Mr Carter has often holidayed in the Cook Islands - but despite suspicion that Mr McCully was exercising his sense of humour with a reference to Mr Carter's "long association" with the Cooks, Mr Carter said he had other connections.

In recent years he had visited as part of the Commonwealth Parliamentary Association. He also recalled being based in Rarotonga in 1995 as a government representative on the HMNZS Tui, which was protecting boats protesting against nuclear testing on Mururoa Atoll.

"I was seasick for four days straight."

Mr Carter's appointment was largely seen as a sweetener offered by Prime Minister John Key before the last election as part of an agreement to stand down.

His Northland electorate is one of the safest National Party seats in the country and has a large party membership.