Drivers of gas-guzzling vehicles are to pay much more for their car tax, announced Chancellor Gordon Brown in the Budget.

But all motorists were spared an immediate rise in petrol prices when Mr Brown deferred a 2p fuel duty increase until October.

Those with the most-polluting vehicles, including some "Chelsea tractor" 4x4s, face a doubling on their annual vehicle excise duty to around £400 a year.

But the Chancellor staggered the increase for vehicles in the highest VED band - band G.

The band G rate will rise by 30% this year to £300 with another hike to £400 in 2008.

Mr Brown said that VED for band B - which takes in "green" vehicles like the Toyota Prius and the Honda Civic Hybrid - would be reduced from £50 to £35.

But cars in band F - which is the second-highest - will pay £10 more this year and £5 for each year after that. Rates for cars in bands C and E will increase by £5 a year for the next three years.

There was another sting for petrol-engined car owners.

Until today VED rates were slightly cheaper for them than for diesel-powered cars.

But Mr Brown said VED would from now on be levied at the diesel rate - meaning another slight rise for many motorists.

The 2p a litre rise in petrol and diesel at the pumps next October will be followed by a 2p rise in 2008 and a 1.8p rise in 2009, Mr Brown said.

RAC Foundation executive director Edmund King said: "Motorists will breathe a sigh of relief that there will be no fuel tax rise for six months.

"There is still great uncertainty in the world oil market and prices are still high."

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