There's more bleak news for Labour leader Andrew Little and his party in a new One News-Colmar Brunton poll

Labour has taken a body-blow in a new poll, falling back to 28 per cent while National surges to 50 per cent.

There is more bad news, too, for Labour leader Andrew LIttle in the preferred prime minister rankings where he slips into third place on 7 per cent against 10 per cent for NZ First leader Winston Peters.

Prime Minister John Key scores 39 per cent as preferred prime minister, down only slightly since February, suggesting his defeat in the flag referendum, which opted to keep the current flag despite Key championing the alternative silver fern motif, has not harmed his popularity..

ELTON RIKIHANA SMALLMAN/FAIRFAX NZ National surged to 50 per cent in the new poll.

The One News-Colmar Brunton poll was taken between April 2 and April 6, straddling the period when the release of the Panama Papers dominated the headlines.

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It also follows Labour's "Future of Work" conference including discussion about a possible universal basic income (UBI).

It puts Labour 4 percentage points lower than a similar poll in February. National has risen three points since then.

Labour is trailing National by 22 points - the same gap as in the 2014 general election where Labour scored just over 25 per cent against National's 47 per cent support.

Key said he was pleased with the latest numbers, but Little said the poll was "disappointing".

"I had a bad couple of weeks a couple of weeks back, which I expect reflects that."

That included his comments about legislating for trading bank interest rate cuts and limiting immigration by ethnic chefs in favour of locally-trained chefs..

The debates about a UBI was also a likely factor, Little said.

But he believed Labour was addressing the right issues.

The public were angry about the Government's approach to the Panama Papers, which had seen Key defend the foreign trust tax regime.

But LIttle said that came towards the end of the polling period and it took longer for such issues "to seep into the public's consciousness more deeply and more broadly".

Among the other Opposition parties in Sunday's poll the Greens recovered two to 10 per cent, reclaiming the third party ranking from and NZ First, which was down one at 9 per cent.

The Maori and ACT parties were steady on 1 per cent.

The poll of 1000 voters has a margin of error of 3.1 per cent.