National has taken a 'Dirty Politics' hit in the latest ONE News Colmar Brunton poll, down two points to 48% while Labour has gained two and is sitting at 28%.

The poll accounts for the effects of Nicky Hager's Dirty Politics book but not this weekend's developments.

The Greens are up another point to 12% and New Zealand First is safely across the line on 6%. The Conservatives are up one to 3% while Internet Mana is down two to 2%. The Maori Party lingers on just 1%.

However this month's revelations have not damaged John Key's standing as preferred prime minister as he climbs two points to 47%.

Labour leader David Cunliffe also lifted two points but is still a long way behind on 12%. Winston Peters is up one on 5%.

The results leave Winston Peters in a strong position with eight seats. National would hold only a very slim majority with the Maori Party, Act and United Future and John Key would need NZ First to be secure.

The margin of error on the poll is plus or minus 3.1%.

The latest poll also asked if people respondents believe John Key when he says he was not personally informed about the release of SIS information to blogger Cameron Slater.

While 41% said they do believe him, 44% say they don’t and 14% said they didn’t know.