No Cabinet backers for Clarke's dramatic 'PM must go' challenge

They dismissed his latest intervention as the lone mutterings of a known maverick and urged him to 'shut up'.

The former Home Secretary's warning that Labour faces 'utter destruction' and Mr Brown could have to 'stand down with honour' did seem to strike a nerve at Westminster.

Lone mutterings: Charles Clarke's call for a change at the top has had ministers rallying to support Gordon Brown and dismissing Clarke as a 'maverick'

But by last night there were no MPs willing to take up his call for a public debate about the Labour leadership.

Mr Brown himself shrugged off the controversy by telling the CBI in Scotland he was 'cautiously optimistic' about Britain's economic prospects.

His prediction of just a short-lived downturn was designed to dispel the damage done by Alistair Darling's gloomy warnings last weekend.

But Mr Brown's speech led to Tory claims that he is at odds with his Chancellor and is glossing over the extent of the difficulties facing the economy.

Shadow Chancellor George Osborne said: 'Gordon Brown says he is cautiously optimistic, while Alistair Darling says the UK's economic problems will be more profound and longer lasting than people expected.

'We have a Labour government descending into civil war and a Chancellor and a Prime Minister who publicly disagree on the severity of the problems we face.'

In an article for the New Statesman magazine, Mr Clarke wrote that there was a 'deep and widely shared concern' within the party that the Government was currently heading for disaster.

He reinforced the message in interviews yesterday when he said the Premier would have to improve or 'stand down as Prime Minister with honour and have a proper leadership election'.

He praised Mr Brown as a ' brilliant Chancellor' but said he had not established his political authority. It was 'entirely possible' for him to 'turn it around' but if he failed to do this  -  and then did not resign  -  the Cabinet would have to decide on a course of action against him.

He said the 'fatalism' of Labour MPs who were resigned to defeat was 'very damaging indeed'.

Asked what should happen if Mr Brown failed to provide clarity and then failed to resign, Mr Clarke said: 'In the event that didn't happen, then I think it would be down principally to the Cabinet to decide how to proceed and what to do and to do that in an expeditious way.'

But he conceded there was no mood in the Cabinet at the moment to do this.

'Many in the Cabinet share the view we are in great difficulty and are doubtful about our capacity of how to get out of it.

'There isn't a view ... that they should go and speak to Gordon in the way I have been describing.'

He ruled himself out as a ' stalking horse' against Mr Brown and he would not advise anyone else to do that because party rules regarding it were 'very cumbersome-and would lead to 'bitter division'.

Labour MPs have been agonising for months about the state of the polls, which show Mr Brown is widely unpopular and the party is 20 points behind the Tories.

They fear an autumn of damaging speculation when the Commons returns in October. Labour also faces a difficult by-election in Glenrothes, the Scottish seat next door to Mr Brown's constituency.