The Greens say a "desperate" Prime Minister John Key has today made "underhand" attacks on the party over partial asset sales because he has lost the public debate.

Legislation to enact the Government's plan to sell up to 49 per cent of state-owned energy companies Mighty River Power, Solid Energy, Genesis and Meridian is due to pass its final stage in Parliament this week.

However, polls continue to show the majority of the public oppose the move.

In two interviews about asset sales this morning, Key attacked the Greens for using $75,000 of its taxpayer-funded leaders' budget to hire staff to collect signatures towards a citizens initiated referendum on the issue.

"These are the people that said they don't have enough money to pay for (deaf MP) Mojo Mathers' technology in Parliament but have enough money for a citizens initiated referendum," he told Newstalk.

"This is a politically-motivated referendum."

A referendum would be non-binding on the Government and wouldn't go ahead until the sales were underway, he said.

The Greens pushed the smacking law through Parliament, Key told TVNZ's Breakfast programme.

A citizens initiated referendum found the majority of people opposed that law which passed through Parliament after then-leader of the Opposition Key struck a deal with Labour to support it.

Greens co-leader Russel Norman said the prime minister was "desperate on asset sales because he has totally lost the public debate".

"So now all he can do is make underhand attacks based on completely false information about the Greens."

Norman countered Key's comment on Mathers, saying the party never said it couldn't afford to pay for her Parliamentary support.

"The problem was that if it became the position that any special requirements for individual disabled MPs became the cost of the party, it creates a disincentive for parties to have disabled candidates."

The Greens had "shot down" all the Government's arguments for asset sales, he said.

"They said the companies need access to capital, but they get no access to capital using this method. They said they had to do it because of the Government's fiscal position but actually it makes the Government's fiscal position worse."

"Every time they put up one ridiculous argument after another for privatisation, we've shown it's not true. That's what the prime minister hates."

Norman conceded the asset sales legislation was likely to pass by one vote but said the Greens would keep campaigning against it and pushing for the referendum.

The Greens had been public from the start about hiring staff to help collect some of the 310,000 signatures required.

"Unlike the Government which won't tell us how much they are paying Senate Communications for spin, Clemenger for advertising and Goldman Sachs for investment banking services."

The referendum on smacking had been confusing but the asset sales question was simply tied to the Government's proposal, he said.

"New Zealanders have a right to have a say on whether the privatisation goes ahead. This is a huge inter-generational issue which will have an ongoing effect."

- © Fairfax NZ News