Nick Clegg has challenged Gordon Brown over compensation for losers from the removal of the 10p tax rate.

Speaking at prime minister's questions in the Commons on Wednesday, the Liberal Democrat leader called for "concrete proposals" to be spelt out.

Ministers are coming under renewed pressure to do so in the wake of last week's disastrous local election results and ahead of the Crewe and Nantwich by-election later this month.

Labour MPs are also threatening to re-ignite their planned rebellion on the government's Finance Bill if the matter is not resolved by then.

And with the issue being thought to have damaged Labour deeply at the polls, Clegg quoted former home secretary Charles Clarke who said this week that the "doubling of the 10p tax rate will 'resonate until there is clarity'.

"When we will get concrete proposals?" he asked Brown.

The prime minister replied that "his party are not proposing the restoration of the 10p rate".

He said that the chancellor had written to the Commons Treasury committee setting out his commitment to help the pensioners and low earners who had lost out.

Alistair Darling "will put forward his proposals in due course", Brown added.

But Clegg said the answer was "not good enough".

The issue was a "matter of principle", he told the prime minister which had shown that "he has got no principles and the Tories have got no policies".

He demanded that compensation be "fully backdated" to the start of the current tax year and that taxpayers will "not have to jump through hoops" in the complicated tax credits system to get it.