Wellington - New Zealand's conservative National Party is poised to sweep from power the Labour-led coalition that has governed for nine years, according to election-eve opinion surveys published Friday.

But the polls indicate that up to 1-in-10 voters are still undecided, and New Zealand's proportional representation system, which is designed to ensure minor parties are represented in Parliament, could still produce some surprises in Saturday's general election.

The last two opinion polls published Friday morning echoed two surveys the previous night showing the Nationals well ahead of Labour and set to win a narrow majority in a new Parliament of about 123 seats, with the support of centre-right allies.

The Greens, who are pledged to support Labour, are tipped to double their strength to 12 seats.

The New Zealand Herald warned: "Small movements in smaller parties could have a dramatic impact on the election result."

Labour Prime Minister Helen Clark, 58, a 27-year parliamentary veteran, was conceding nothing and appealed to "true believers in the heartland" to vote to save her government.

The Nationals' leader John Key, 47, who made a fortune as a foreign currency dealer before turning to politics six years ago, claimed to sense "a strong mood for change."

If the margin between Labour and the Nationals narrows in the last day of frantic campaigning by both sides, the Maori Party - formed only four years ago to represent the country's 565,000 indigenous people - could hold the balance of power.

The Maoris will not say who they would support in that case and will consult members at a series of meetings around the country before deciding.

"We are not left or right - we are here to advance the aspirations of Maori people in the interests of this country," said co-leader Tariana Turia, a 64-year-old grandmother who founded the party in 2004 after quitting Labour over policy differences.

The party's other co-leader, Pita Sharples, 64, a portly grey- bearded anthropologist, favours supporting Labour, which with guaranteed support from the Greens gives Clark her best hope of surviving for another three-year term.

Turia said that she trusts neither Clark, whom she served as a minister for four years, nor Key: "I will work with the devil if I have to."

In a campaign dominated by the worsening international financial crisis, Clark stressed her experience: "It's time for strong and proven leadership - it's no time to switch horses in mid-stream."

Key shrugged off his lack of political experience, saying his time overseas with the US bank Merrill Lynch equipped him to deal with the ongoing crisis and its impact on New Zealand's economy.

Both have strived to out-bid each other with billions of dollars of promises for every sector of the economy and community, tax cuts and growth stimulus packages to fight off the worsening recession and rising unemployment amid forecasts of a decade of budget deficits to come after years of surpluses.

The Nationals have gathered public support for more than a year as Key moved to position his conservative party in the centre, while Clark antagonized voters with policies allowing civil marriages for gays, outlawing parental smacking and legalizing prostitution.

Key has said he would welcome the free-market ACT party - which advocates slashing public spending, selling state assets and competitive health and education sectors - as a coalition partner.

He has ruled out a cabinet post for ACT founder Sir Roger Douglas - architect of the 1984-90 Labour government's sweeping economic reforms, who is bidding to return to Parliament at the age of 70 - because of his "radical right-wing views."

Key, a father of two, restored the art of kissing babies to the campaign, presumably to present a caring image to voters as well as to draw comparisons with Clark's childless status.

But Clark sneered: "There's no such thing as compassionate conservatism - we have got no history of it in New Zealand."

If the outcome is closer than the polls indicate, the possible combinations in the next government are complex, given that both main parties have ruled out certain partners.

Key's Nationals will work with ACT and Peter Dunne, leader of the United Future party, who was a minister in the last Clark government but is changing sides after sensing a Labour defeat.

Key has ruled out working with Winston Peters, leader of the nationalist New Zealand First party, who was foreign minister under Clark until he stepped down pending a series of investigations into secret donations.

If Clark is in a position to form a government, she will welcome the Greens into a coalition for the first time, but they refuse to work with Peters, whom she has not ruled out, though she would prefer he disappears into political oblivion, as current polls suggest.

Nearly 3 million voters will choose between 682 candidates and 19 parties for the Parliament of about 120 seats. Just under 230,000 of the voters are Maoris, who will vote for the seven Maori seats.