Voters have turned on the O'Farrell government and are threatening to throw it out of office after just one term in a dramatic resetting of the political contest in NSW.

Three years after Barry O'Farrell was swept to power after an historic rejection of the long-serving Labor government, the latest Fairfax-Nielsen poll shows Labor is leading the Coalition 51 per cent to 49 per cent on a two-party preferred basis. The turnaround represents a 15 per cent swing since the March 2011 election and is the first time Labor has led the Coalition since 2008.

Labor's primary vote, which crashed to an historic low of 25.6 per cent in 2011, has recovered to 35 per cent - an improvement of 12 points since the last Nielsen poll in March 2013.

The Coalition's primary vote has fallen to 40 per cent from 51.2 per cent at the last election - down 12 points since last year's poll.