Treasurer Wayne Swan during Question Time at Parliament House in Canberra on Tuesday 30 October 2012.

Treasurer Wayne Swan during Question Time at Parliament House in Canberra on Tuesday 30 October 2012. Photo: Alex Ellinghausen

Opposition Leader Tony Abbott has turned his focus away from the carbon tax and is attacking the government over its forecast budget surplus.

Amid backbench concerns that the carbon tax argument has run out of steam, and in the face of Labor's improving polls, Mr Abbott yesterday targeted the government's economic credentials, throwing doubt on the surplus.

''I regret to say that this is highly unlikely, indeed becoming increasingly impossible, under the current government,'' he said.

''The current government is crab-walking away from the promised surplus.''

In Parliament, carbon tax questions were abandoned in favour of an opposition grilling over the forecast surplus.

Mr Abbott again asked Prime Minister Julia Gillard if she could guarantee a budget surplus in 2012-13.

Ms Gillard referred to the midyear economic and fiscal outlook, saying the government was on track to deliver the revised surplus - down from $1.5 billion to $1.1 billion.

Treasurer Wayne Swan backed up the Prime Minister, saying delivering a budget surplus was still the plan. ''We are bringing our budget back to surplus, and we stand absolutely by all of the forecasts that were contained in the midyear budget update,'' he said. ''We could not be clearer than that.''

The Treasurer said the global economy would be a factor, but it was important to get back in the black in order to give the Reserve Bank flexibility over the interest rate level.

But shadow treasurer Joe Hockey tried to suspend proceedings in order to condemn the government over its forecast surplus, saying Labor was being deceitful and would never deliver it.

Mr Hockey said Ms Gillard and Mr Swan had continually watered down their references to the surplus - from a promise, to a guarantee, to a plan.

''This is a government that has now reached new heights. Today, the commitment to a surplus became a plan,'' Mr Hockey said.

''Today, the Prime Minister said it is on track. Previously, the commitment to a surplus was a wholesome promise - it was a guarantee, it was in the budget …

''The Australian people have had enough of the deceit … The Australian people have had enough of promises and plans, commitments - all the other weasel words. The bottom line is that the Labor Party must deliver. It must actually deliver on its words if it is to be trusted.''