Key Points:

National's decision to freeze any state asset sales, including partial share floats, has been savaged by Prime Minister Helen Clark as "laughable".

National leader John Key said yesterday that in the first term of a National government, no state assets would be sold or partially sold.

The party's policy last election was to allow for a quarter of the state-owned enterprise Solid Energy to be floated and for farms held by LandCorp to be sold.

Helen Clark in her speech to the Labour Congress on Saturday described state asset sales as a "defining issue".

She made reference to the ministerial veto of a 40 per cent sale of shares in Auckland International Airport; the buyback of Air NZ after it had been privatised, the buyback of the nation's rail tracks, and negotiations with Toll to buy back rail services.

National said it would have accepted the advice of Overseas Investment Office officials to approve the sale of Auckland Airport.

The party has recently announced that strategic assets should be 51 per cent owned by New Zealanders.

And Mr Key sought to neutralise the potency of the state asset sale issue with his announcement yesterday on Agenda of a freeze on sales in the first term of a National government.

"If there's any change to that position, then we'll come back to the people of New Zealand with transparency and seek a mandate for that."

He said asset sales would distract National from "the real agenda of lifting after-tax wages in New Zealand".

Mr Key's caveat that it was a one-term policy invited scorn from Helen Clark.

"It's laughable, isn't it? The promise seems to be they'll spend the whole first term working on it and then really get down to business selling the family silver in the second."

She said the policy announcement was a very powerful campaign tool for Labour. She rejected a suggestion that Mr Key's policy had taken asset sales off the agenda. "Absolutely not. He has put this issue squarely on the agenda. National wants to sell the family silver; Labour doesn't.

"Mr Key's whole history as leader of the National Party over the last 18 months or so has been one of "flip-flop, flip-flop, flip-flop.

"I don't think he really remembers what he said yesterday."

Attacks on Mr Key were a large feature of the Labour Party congress in Wellington over the weekend.

Helen Clark did not mention him during her speech on Saturday to a crowd of 600 but peppered it with criticisms of National, saying that Labour's achievements in its eight and a half years in Government, such as KiwiSaver and Working for Families, could only be guaranteed by Labour.

The more gritty attack on Mr Key was delivered by Deputy Prime Minister Michael Cullen yesterday.

"Mr Key is a politician who is proving to be very much less than the sum of his parts," he said.

He cited a series of issues in which Mr Key's responses had been unclear, inconsistent or had changed, including his view of the Springbok tour, the war in Iraq, the Civil Union Bill, climate change, a deadline for Treaty settlements and assets sales.