GORDON BROWN was forced into another embarrassing tax U-turn last night when he bought off a threatened Labour revolt on plans for big tax hikes on “gas-guzzling” cars.

A Conservative attempt to prevent the tax increases applying to all vehicles bought since 2001 failed in the Commons when just six Labour backbenchers – including Walton’s Peter Kilfoyle – backed a key amendment.

But the rebellion was only averted after ministers, such as Wallasey’s Angela Eagle, and whips were scrambled to promise Labour MPs a rethink on the policy in the autumn.

Details were sketchy, but one idea being floated was to phase in the higher taxes over a longer period – giving car-owners longer to sell their current vehicle.

Around 50 Labour MPs have protested it is unfair to make car tax changes retrospective. They have also warned it will be hugely unpopular and repeat the 10p tax rate fiasco. According to Tory figures, more than 2m motorists will be between £100 and £245 worse off from next April – twice the number of people still losing out because of the scrapping of the 10p band.

Furthermore, owners of older, family cars – such as the Citroen C8, the Renault Espace and the VW Passat – will be hardest hit, seeing their £210 car tax rise to £430 or £455 by 2010, the Conservatives said.

Publicly, No.10 said there would be no climb-down, insisting “difficult decisions had to be taken sometimes to show how serious we are about the green agenda”.

Ronnie Campbell, the Labour MP leading the revolt – who had threatened to vote with the Tories – announced he had changed his mind after “getting an assurance from the whips office”.