A poor result on a new political poll has added to Labour's woes today.

Labour has dropped six percentage points to 23 per cent in the stuff.co.nz/Ipsos political poll. National rose to 56 per cent - a result that would let them govern without a coalition partner.

The polling took place early in the week before the revelation that David Cunliffe wrote a letter in support of Donghua Liu's residency application in 2003.

The poll showed results for Mr Cunliffe as preferred prime minister slipped two percentage points to 11 per cent, while results for Prime Minister John Key to remain as prime minister rose three points to 51.4 per cent.


In February, 81.6 per cent of respondents to the same poll who had voted for Labour in 2011 said they would vote for them again in September.

In the latest poll this number dropped to 61.3 per cent, with the greatest drop in support affecting 30- to 44-year-olds.

Ipsos managing director Matt Benson told Fairfax that previous Labour voters were now unsure who to vote for.

"An increase in alternate party activity on the Left side may have traditional Labour voters weighing up their options and thinking again about Labour.

On the other side, as the party options for conservative voters reduce, we are seeing them flock to National.