WELLINGTON, Oct 20 (Reuters) - New Zealand's Green Party said on Monday it will not do a deal to support a National-led government after next month's election, but will require significant policy concessions to support any Labour-led administration.

The Greens, who currently have six seats, are likely to be the biggest of the minor parties in the Nov. 8 vote and might be crucial in the formation of a minority coalition government.

The party said there was little separating the two main parties, but National, which is well ahead in polls, would take New Zealand in the wrong direction.

"This means that we cannot form a government with National, or support them on confidence and supply, although we could work with them in areas where we have common ground," said Greens co-leader Jeanette Fitzsimons.

The Greens have not formally backed the current Labour-led coalition government, but have been neutral on no-confidence motions and on occasions have wrung concessions and spending promises in return for support on some legislation.

It backed Labour's recently passed carbon trading scheme in return for a commitment to spend NZ$1 billion over 15 years insulating old houses, which National has since said it would scrap.

However, Fitzsimons said the Greens could join or support a Labour-led government on the right terms.

"Whether we could form a government with them would depend on reaching a policy agreement that advanced green policies on a number of fronts," she said.

The National Party continues to have a large lead over Labour in latest opinion polls, although the gap has narrowed slightly. A Reuters survey <NZPOLL> of five leading polls has National with a 14 percentage point lead over Labour, which is seeking a fourth three-year term.

Under New Zealand's proportional representation electoral system, a party must win either a local district electorate or 5 percent of the nationwide vote to get a seat in the 120-seat, single chamber parliament.

The Greens have 6.8 percent backing in the Reuters survey, which if carried through to election day would see them increase their number of seats.

The outgoing Labour government was backed by the small centrist New Zealand First and United Future parties, both of which demanded the exclusion of the Greens as a condition of their support. (Reporting by Gyles Beckford; Editing by Bill Tarrant)

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