Prime Minister Gordon Brown was today facing the prospect of another damaging rebellion by Labour MPs over tax.
Backbenchers urged Chancellor Alistair Darling to re-think plans announced in the Budget for big increases in vehicle excise duty on "gas guzzling" cars.
Although vehicles bought before 2001 are exempt, MPs are concerned that the some owners who bought bigger cars in the past not realising the changes were on the way, could be faced with increases of up to £200.
More than 30 Labour backbenchers have now signed a Commons motion urging ministers to re-think the proposals before the new rates come into force.
But as some Labour backbenchers were calling for Brown to quit, five Cabinet Ministers rallied to Gordon Brown’s defence.
Labour MP Ronnie Campbell, who tabled the motion, warned that the impact of the increases could be similar to scrapping the 10p tax rate, which led to Mr Darling’s £2.7 billion climbdown in an emergency "mini budget" earlier this month.
"It is unfair (on) people who bought their cars a few years ago not knowing that the Government were going to put this road tax on," he told BBC Radio 4’s The World at One.
"When people get their road tax letter through the door next year and find they have got an extra £200 to pay – well, I don’t have to say any more, do I? The motorist is taking the brunt again."
Mr Campbell, who is due to meet Mr Darling when MPs return to Westminster after this week’s Whitsun break, also called on Mr Darling to drop the planned 2p increase in fuel duty due in October.
He said that with rising world oil prices pushing up prices at the pumps, another increase would be too much for many families.
The demands represent another headache for Mr Darling and Mr Brown at a time when the Prime Minister is already politically weakened by the debacle over the 10p tax rate and Labour’s disastrous performance in the council elections and the Crewe and Nantwich by-election.
At the same time, the £2.7 billion emergency compensation package for people hit by the abolition of the 10p rate has left the Chancellor virtually no room for manoeuvre with the public finances.
Ministers were today talking tough.
Environment Minister Joan Ruddock dismissed suggestions that the increases in vehicle duty had come as a bolt from the blue.
At the same time she said that the Government could not afford to abandon its environmental agenda for tackling climate change.
"I think the direction that we have all been going in has been clear to people for some time," she told The World at One.
"These things are all a matter of balance. What we cannot afford to do is to lose sight of the environmental agenda because this is everybody’s future. This is the future of the planet.
"We have got to have measures – we can be smarter about them – but anybody who suggests that this environmental agenda can go away is talking nonsense."
There have been private mutterings that Labour needs a ‘Cameron clone’ to take on the Tories.
But senior figures spoke out on behalf of the embattled Prime Minister.
Significantly, two of those who rode to the rescue – Foreign Secretary David Miliband and Health Secretary Alan Johnson – are widely touted as potential successors to Mr Brown.
Others wheeled out for the public show of unity were Chief Whip Geoff Hoon, Cabinet Office Minister Ed Miliband and International Development Secretary Douglas Alexander.
They insisted that Mr Brown remains the ‘best man for the job’ as they tried to quell speculation that Labour’s high command is ready to move against the PM.
The public protests of loyalty and support failed to mask the agonising at the highest levels about how to save Labour from a mauling at the next General Election.
Cabinet members are aware, and increasingly worried, that things are not working out amid claims that up to 40 backbenchers are ready to back a challenger to Mr Brown.
None of the serious contenders, such as David Miliband, Work and Pensions Secretary James Purnell and Justice Secretary Jack Straw, will strike.
But if Mr Brown were to fall on his sword, any declarations that they are not interested in the job would be deemed null and void and each would almost certainly move.
Yesterday David Miliband was forced to describe as ‘fiction’ reports that he is preparing a leadership bid. ‘I am not in themarket for any job other than the one I have at the moment,’ he said, although he did not explicitly rule himself out of standing should a vacancy emerge. ‘We have got to show we are up for the fight. We have got to pull together.’