French prime minister Manuel Valls has made a flying visit to New Zealand, discussing Rainbow Warrior and Helen Clark.

France's Prime Minister Manuel Valls says the bombing of the Rainbow Warrior by French agents in Auckland in 1985 was a "huge mistake".

Valls said in a press conference at Auckland Museum on Monday that "30 years ago our relationship was quite challenging".

"We had made a huge mistake. We have turned over a new leaf and we are facing toward the future."

PETER MEECHAM France's Prime Minister Manuell Valls met with John Key during his visit to New Zealand.

Valls' one-night trip to New Zealand was the first visit by a French Prime Minister since 1991 when Michel Rocard came to apologise for the Rainbow Warrior bombing.

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The bombing claimed the life of photographer Fernando Pereira and was the first time an act of international state-sponsored terrorism had been committed in New Zealand waters.

Prime Minister John Key said the incident was mentioned by Valls at a dinner on Sunday night.

"It was probably important for him to raise rather than for me to raise as the host," he said on Monday.

"Hindsight's a wonderful thing. I'm sure they would never repeat that.

"In the end the relationship has to be stronger than one particular thing that was a big mistake by France and we have to look forward and put those things behind us."

Key said Valls did not strictly offer an apology: "I just think he phrased it that it was a big mistake and I think there's real regret on the French side."

Key used the visit to lobby the French on former New Zealand Prime Minister Helen Clark's bid to be UN Secretary-General.

Valls praised Clark as a great candidate but was diplomatic in saying that there were many nominations to consider.

He said it was too early to say which way France - as one of the five permanent members of the UN Security Council - would vote.

Key said the pair had a great discussion about Clark.

"I think it's pretty fair to say there's zero chance of the French vetoing Helen Clark and I think a pretty good chance under the right circumstances that they would support her. They certainly knew the work that she's done and the role that she's played."

The visit to Auckland involved a traditional Maori welcome for Valls and the visiting French delegation and a wreath-laying ceremony at the Auckland War Memorial Museum cenotaph.

Valls left on Monday morning to take a private jet to Canberra, where he was due to meet Australia's Prime Minister Malcolm Turnbull to talk about a major submarine contract that has been won by a French shipbuilder.