Labour MP Phil Goff says he'll take leave of absence from Parliament when he campaigns for the Auckland mayoralty.

Mr Goff yesterday announced his candidacy for the mayoral election next October.

He has set out his broad plans, telling supporters he would focus on solutions to traffic congestion and on building more homes.

Rival mayoral candidate Mark Thomas said that if Mr Goff was serious about running, then he should resign from Parliament straight away and fully commit to the campaign.

Mr Thomas - a former National Party candidate for Parliament - said he thought it was impossible for Mr Goff to do an 80-100 hour a week job as an MP and campaign with all the effort needed to become Mayor of Auckland.

But Mr Goff told Morning Report today nobody campaigned for 10 months, and he would take leave when he did campaign full-time, about a month before the election.

"I was able to hold down the jobs of Minister of Justice, Minister of Foreign Affairs, and MP for Mount Roskill by working extraordinary hours. That's what I've done, that's what I'll continue to do. My first priority, the job I get paid to do, is being MP for Mt Roskill. That comes first."

Labour Party leader Andrew Little said he was confident Mr Goff could continue to fulfil his role as an MP while also campaigning for the mayoralty.

Mr Little said it was always possible that if Mr Goff started to struggle with the workload, he could ask him to reassess his position as an MP.

Mr Little says Mr Goff is relinquishing his Auckland issues portfolio, so there'll be no confusion about whether he has his MP's or candidate's hat on.

Mr Little said he had discussed the leave of absence of Mr Goff.

"I think that's the right thing to do. I don't think he needs to leave any earlier than when he is declared the new mayor of Auckland."