Prime Minister John Key has declined to comment on carbon pricing in Australia but says his government will be capping its floor price at $25 a tonne.

The New Zealand government on Monday announced it will be putting a stalemate on ETS price rises and excluding agricultural sector emissions until at least 2015.

That will involve keeping a $25 fixed-price option until at least 2015.

Mr Key said that decision was made to put a lid on pressure on the economy.

His comments came amid speculation that Labor is considering lowering the $A15-a-tonne carbon floor price for the ETS, set to replace the carbon tax in mid-2015.

Earlier, Deputy Prime Minister Wayne Swan did not rule out scrapping the floor price down the track.

"I'm not getting into the hypotheticals of that - we've got a fixed price for three years," he told reporters in Brisbane.

Mr Key said it was up to Australia to apply what ever carbon policy it thought best.

"It's a matter for Australia what domestic policies they apply," he told reporters in Sydney.

"Our scheme is already in operation, it's not like we don't have one.

"But we thought the environment was too fragile internationally, and to put further costs on New Zealand consumers at this time could threaten jobs."