Grey Power and students have stood together in Wellington to front a citizens-initiated referendum opposing the sale of state-owned assets.

"People are swarming to sign this petition," Grey Power president Roy Reid said, as the petition was launched on Thursday morning.

His members think power prices will rise if energy companies are partially privatised, and many go to bed to keep warm now because they can't afford power bills.

"This rot has to stop," he said.

New Zealand Union of Students' Association vice-president Arena Williams said the government was "selling our country from under our feet", and it was brilliant to work with Grey Power.

Labour leader David Shearer said the groundswell against asset sales was enormous, while Greens co-leader Russel Norman said the country needed a leader as a prime minister and a vision for the future.

"This is our line in the sand," said New Zealand First MP Brendan Horan.

A referendum will be held if the petition is supported by 10 per cent of voters, which means they have to collect about 300,000 valid signatures.

The organisers are confident they will meet the target.

The result of the referendum won't be binding on the government but it will be a powerful demonstration of how the public feel about its plan to partially sell energy companies and sell down its stake in Air New Zealand.

Prime Minister John Key has said the election result has given them a mandate to go ahead with the partial sell-off of state assets.