Nick Clegg calls for one-off tax on fortunes of the super rich

Deputy Prime Minister's move set to reignite Tory anger after summer of friction in Coalition

A radical one-off tax on the fortunes of the rich has been proposed by the Deputy Prime Minister Nick Clegg in a move set to anger Tory backbenchers before the new political season has even begun.

Warning that the UK had become mired in "a longer economic war rather than a short economic battle", the Liberal Democrat leader said in an interview that "people of very considerable personal wealth have got to make a bit of an extra contribution".

"In addition to our standing policy on things like the mansion tax, is there a time-limited contribution you can ask in some way or another from people of considerable wealth so they feel they are making a contribution to the national effort?" he asked rhetorically. "The action is making sure that very high-asset wealth is reflected in the tax system in the way that it isn't now."

The idea is likely to raise the hackles of his Coalition partners, especially as it has been floated at the end of a summer which has seen the greatest friction yet between the two parties in power.

Indeed, Mr Clegg admitted in his interview with The Guardian that he had not "found it very easy to make progress with the Conservatives" on the issue. This, he said, was because they did not fully recognise the impact of the double-dip recession meant "taking pretty difficult decisions which some people will not like".

However, he voiced support for Chancellor of the Exchequer George Osborne and the Government's cuts to public spending to rein in the deficit, which he implied were necessary. "The caricature of what George Osborne is doing on the fiscal side is absurd," he said. "If you read some of the commentary, particularly from the left, you would think he was turning the clock back to the 1930s."

He added that he believed the problems resulting from the UK's "broken banking system" were severe enough that Westminster should examine the possibility of setting up a "business lending bank with direct or indirect support from the government".

Though the Deputy Prime Minister conceded he and his party had both lost "a significant amount of support" through the "calculated collective gamble" of governing with the Conservatives, he said they had to forget the past and aim for the "sunny uplands".

"Frankly, there are a group of people who don't like any government in power and are always going to shout betrayal. We have lost them and they are not going to come back by 2015. Our job is not to look mournfully in the rear-view mirror and hope that somehow we will claw them back. Some of them basically seem to regard Liberal Democrats in coalition as a mortal sin."

Mr Clegg also said in blunt language that the Tories much hoped-for constituency boundary reforms, which they argue would rid general elections of an inbuilt imbalance in favour of Labour, was dead because of the Conservative rebellion that scuppered House of Lords reform.

"It is not going to happen, because we are not going to support it," he said. "A deal is a deal.

If you have a contract and one person says 'I am sorry I can't honour my side of the contract', it is perfectly reasonable for the other side to say 'I will slightly tweak my side of the contract'. People understand that is how coalitions work."