United Future leader Peter Dunne has played the "sensible" card, saying only his party can moderate ACT or the Greens' influence over the next government.

The Greens yesterday ruled out supporting a national-led government -- setting up a Labour-Greens, National-ACT left-right split.

Mr Dunne said today only United Future could provide a "sensible moderating influence" on either of those possible combinations.

United Future has said it can work with either main party and will negotiate first with the one that wins the most votes.

Mr Dunne said if National needed ACT to form a government, New Zealand could expect to see the party's founder and finance spokesman Sir Roger Douglas back in Cabinet despite National leader John Key's protests to the contrary.

"A backward step to the policies of 1984 will see soaring mortgage interest rates; health and education services privatised; most state assets flogged off to the highest bidder; welfare services savagely slashed and the triumph of corporate greed over public good."

He said a Labour-Greens government had the potential to destroy the economy.

He blamed the Greens for the emissions trading scheme -- even though the initiative was the Government's -- which he said would destroy the dairy industry.

The Maori Party is refusing to express a preference for either main party, but a large proportion of its supporters give Labour their party vote.

Mr Dunne said the Maori Party's main interest appeared to be setting up a "state within a state".

The Greens said yesterday they would require significant policy concessions to support a Labour-led government