Prime Minister John Key is refusing to commit to a referendum on asset sales before the first share float.

Labour and the Greens claim they are on track to collect enough signatures to force a referendum - but Mr Key yesterday said they still had some way to go.

The petition, calling for a halt to the sale of shares in the state-owned energy companies and Air New Zealand, needs 310,000 signatures to force a citizens-initiated referendum and has about 250,000 so far.

Labour and the Greens say they will have enough signatures by the end of the year. The Government will have 12 months to respond once the signatures are verified.

Mr Key yesterday questioned whether all the signatures collected so far were legitimate - and said their authenticity would be tested "very thoroughly" before a decision on a referendum was made. A referendum next year could coincide with a round of share floats.

But Mr Key said the public had already had a chance to have its say.

"We had the biggest referendum we're going to have, which was a general election."

Green Party co-leader Russel Norman said the Government's asset sales programme was in crisis and a referendum should be held as soon as possible once the signatures were collected.

Mr Key will say on Monday whether the Government will bow to a Waitangi Tribunal request to defer the asset sales after the tribunal concluded Maori had a proprietary type interest in water.

He was confident the partial share float was still on track.

"All of these things, in terms of people testing their rights, potential court action, the Waitangi Tribunal deliberations, all of these things are highly predictable."

Finance Minister Bill English said the Government was carefully working its way through the legal issues. "We've always said we would expect to end up in the High Court and so now we've got this particular report from the tribunal we have to have a look at the way they've couched the issues and how we would consider them and how a court might consider them."

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