THERE could not be a worse time to abandon the Coalition's austerity programme, Danny Alexander, Chief Secretary to the Treasury, will declare today.

He will make the claim after Liberal Democrat sources mooted the idea of introducing extra council tax bands for expensive property as an alternative to the mansion tax.

In his keynote speech to party conference, the Highland MP will brush aside calls made by Labour and the SNP for a Plan B – rejected by delegates in a vote yesterday – to pump billions of pounds into new capital investment projects and declare that the UK Government's austerity programme is the only foundation for future growth.

He will say: "We have rebuilt the confidence in this nation's ability to pay its way in the world, we can now put that credibility to work for the British people.

"There could not be a worse time to argue that we should abandon our plan. "

Mr Alexander will say it was the "right, pragmatic" response to worsening growth forecasts for the Coalition to push some spending cuts into the next parliament.

Meanwhile, it has emerged that Nick Clegg has suggested the creation of two or three new council tax bands on high-end properties across the UK as an alternative to the proposed 1% annual mansion tax on properties worth more than £2 million.

Party sources suggested the plan could hit the same householders as those who would be affected by the mansion tax. Chancellor George Osborne is thought to be open-minded about the proposal while Prime Minister David Cameron is more hostile.

The proposal would not mean a complete revaluation of properties but simply introducing two or three new tax bands for expensive homes north and south of the Border.

Elsewhere in his speech today, Mr Alexander will warn wealthy tax dodgers that "we are coming to get you".

He will reaffirm his commitment to tackling tax avoidance and evasion, saying the Government is on track to raise £4 billion this year from a £900m investment announced two years ago.