Labour leader David Cunliffe has delivered a belated acknowledgement that it was a mistake not to work more closely with the Green Party and lashed out at Kim Dotcom as "reprehensible."

Asked if Mr Dotcom had affected the chances on the left, Mr Cunliffe said "absolutely."

"For anybody to wade into New Zealand politics, spend over $4 million and end up wiping out his own supporters and damaging the left I think is reprehensible."

He said it had made life more difficult for Labour and the Greens.

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"Can I say I very much hope in the interests of all New Zealanders, and the interests of the progressive side of politics that we are not again in a situation where the left vote is splintered, that we work in a much more cohesive way and we take a clear and united alternative government to New Zealanders."

ELECTION INTERACTIVE: Every vote, every seat, every result

Mr Cunliffe also conceded it may have been a mistake not to take the Green Party up on the offer to campaign as a joint force in the election. He did not believe the parties should merge "but I do think there is potential for us to operate in a more cohesive way."

"In hindsight, the progressive forces of politics probably would have got a better outcome if they had been better coordinated."

Mr Cunliffe also indicated Labour had struggled with its own fundraising, citing that as a factor in its defeat. "We can't fight and win a modern 21st Century general election without a higher level of financial backing."

Mr Cunliffe said he was not blaming it all on Dotcom - there was a range of issues to look at. 'We need to go through a very very deep process of reflection about the capabilities of our party and our movement so we can take a clearer set of messages to the public in 2017."

Mr Cunliffe said securing six out of the seven Maori seats was 'the bright spot in a dark night."

Cunliffe seeks renewed mandate

Meanwhile, months of more controversy and instability are looming for the Labour Party Mr Cunliffe said he will call for a vote on his leadership and contest the job again but will not commit to resigning from Parliament if he is defeated in any challenge.

Mr Cunliffe also said this morning that he now regrets not forming a closer alliance with the Green Party during the campaign. The Greens had sounded Labour out about a combined front but was spurned by Labour as it sought to bolster its party vote.

Mr Cunliffe said he will meet with party officials and caucus soon to work through the process required.

The party's constitution requires Mr Cunliffe to pass a 60 per cent confidence vote in caucus within three months of an election or a leadership challenge is triggered.

He said no other MPs had told him they intended to challenge -- but today Grant Robertson and David Shearer would not rule it out publicly.

Mr Cunliffe said he expected party members and union affiliates would get the chance to vote on his leadership. "I will be seeking a renewed mandate for change as leader of the Labour Party."

He hoped it would go to the wider ballot and the matter would be decided by Christmas. Mr Cunliffe secured support of only about one third of caucus when he took over as leader a year ago, but got strong support from party members and union affiliates who had 60 per cent of the vote between them.

Mr Cunliffe would not say if he had given any consideration to resigning on the back of the dismal result, saying only he had considered a range of options. "I believe this is the right way forward. The feedback I've had widely across the party has been that I have the vision and have proven myself on the campaign trail."

However, he indicated he would not resign as an MP altogether if he was defeated to clear the way for a new leader, saying "that is getting way ahead of ourselves."

"I am the servant of the party and I have every intention of continuing to serve it."

Mr Cunliffe also denied that he was not taking proper responsibility for Labour's result -- which he has also attributed to issues such as Kim Dotcom and Dirty Politics dominating the campaign, the comparative stability of National and fundraising issues in Labour. He believed he was best placed to take on a mandate for change.

"There is a strong case for unity and stability in the leadership while we undertake the process of change the party needs."

Asked if he took any responsibility for the instability in the party during the reigns of his predecessors David Shearer and Phil Goff, he said "I do not believe I have ever acted disloyally or outside the interests of the party."

Mr Shearer referred this morning to being undermined from behind in his reign -- an apparent reference to Mr Cunliffe.

View: Election night photo gallery:

Read more of the Herald's election coverage here:

Election results 2014: Metiria Turei - It was Labour's mistake

Jamie Whyte: Act brand is 'tarnished'

Election 2014: Kim Dotcom says he 'poisoned' Internet-Mana

Election 2014: Cunliffe defends decision to stay on

Election 2014: Election delivers moment of truth

List of successful MPs

Colin Craig has spent $2.75m of his own cash on elections but never won a seat

John Armstrong: Cunliffe 'misread the public mood'

Tau Henare: A dramatic election for Maori voters

John Armstrong: Utter triumph for John Key