CLIMATE Change minister Greg Combet has warned Tony Abbott's promise to repeal the carbon tax will threaten Australia's sovereign risk rating because of the major uncertainty created by the move.

In a speech to the Citigroup conference, Mr Combet attacked the opposition's climate change policy which centers on a direct action plan rather than Labor's planned transition from the carbon price to an emissions trading scheme in 2015.

Mr Abbott has promised to scrap the carbon tax, now set at $23 a tonne, if he wins the election due next year.

However, Mr Combet said businesses and industry leaders were now supporting the carbon tax after the "sky didn't fall in" once it came into effect in July this year.

"It creates so much uncertainty, people are making very large investment decisions in the energy sector for example in assets with a life of 30 to 50 years," he said referring to the coalition's plan.

"If he (Mr Abbott) is doing what he proposes then it creates uncertainty and people will stand back and go 'what's going on here?'.

"Those investors are international investors and they know what's going on. They know the carbon prices around the world, they know it's inevitable and they know that this is rational policy response."

Mr Combet said he would campaign against the opposition's carbon policy "every day until the next election".

http://www.theaustralian.com.au/national-affairs/carbon-tax/carbon-tax-repeal-a-threat-combet/story-fndttws1-1226502216470