Trevor Mallard in his beloved Wainuiomata. Mallard is stepping down as electorate MP for Hutt South.

The Labour Party's "attack dog" Trevor Mallard is hoping to become a parliamentary police officer.

The long-serving MP has announced he will not be seeking re-election for Hutt South, in a bid to win the Speaker's job after the 2017 election. To become Speaker, Labour will have to be able to form a government.

He said that, having greatly enjoyed being the assistant speaker, he wanted the top job and would be seeking a spot on the Labour Party list.

CAMERON BURNELL / FAIRFAX NZ Trevor Mallard would like the Labour Party to look for his successor as soon as possible.

But Prime Minister John Key said Mallard was "waving the white flag" because of National rival Chris Bishop's high profile in the Lower Hutt seat.

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Mallard said the assistant speaker role had been "a bit of a change for me. I've had to move away from being a bit of an attack dog to being seen to be non-partisan. What has become clear is that it is hard to be an effective electorate MP and chair the House in an unbiased manner."

He likened the role of Speaker to refereeing your own rugby team.

"I really love the electorate work … it is really hard to be one minute asking a minister to do something for your electorate and the next minute being strict and making sure they are following the rules in the House."

Asked on Monday afternoon what the announcement had done to National's chances in Hutt South, Key said: "Definitely improved. I think what's happened actually in Hutt South, even though Trevor Mallard won't want to admit it, is that [list MP] Chris Bishop has probably been one of our most active MPs.

"You've seen him establish the office in Wainuiomata; he's been running local campaigns on a variety of issues like free parking; he's been extremely active. And I think, to be quite frank with you, Trevor Mallard's waving the white flag."

Mallard told his electorate workers the news on Saturday night, and would not speculate on who the next Labour candidate might be.

As well as concentrating on becoming Speaker, Mallard was also motivated by a desire to ensure there was new blood in the party.

He has been MP for 30 years and said there had been little change among Wellington MPs in recent years.

The decision to stand down was not an easy one, and he had been thinking about it since Christmas.

He has previously denied rumours linking him to the Lower Hutt mayoralty.

Comments on his Facebook page include one from Noeline Colman, whose husband Fraser Colman held the seat from 1967 to 1987.

"That is a shock to the system Trevor. All the best you deserve it."

Bishop paid tribute to Mallard as a long-serving and hard-working MP.

"I just need to pay tribute to his years of long service," he said. "He has been a very staunch advocate for the Hutt Valley and most people would agree he has been a good MP."

The two men have always got on well. Bishop, however, recently showed how serious he is about winning by opening an electorate office in Mallard's heartland of Wainuiomata.

Bishop noted that, for Mallard to become Speaker, Labour would have to win the election.

His rival would make a good Speaker, but he remained confident National would win.

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