Chancellor Alistair Darling has sought to "ease the pressure on family incomes" by introducing his 3p a litre fuel rise in three stages.
Mr Darling said the first 1p rise would be in April, with another 1p increase in October and the last happening in January 2011.
Professor Stephen Glaister, director of the RAC Foundation, said: "At last there is some relief for cash-strapped motorists who over the past year have seen the pump price of unleaded leap by 26.4p to almost record levels.
"With nine out of 10 passenger journeys taking place on the roads, and with 28.5 million cars in Britain, every household in the land has felt some financial pain.
"Drivers spend about 15% of their disposable income on motoring and when it comes to fuel prices, every penny really does count."
Under a previously-announced measure, owners of newly acquired, high-polluting cars will pay a "showroom tax" from next month, which will in some cases more than double the amount of their vehicle excise duty (VED) car tax for the first year of their vehicle's life.
For example, owners of the highest-polluting vehicles will have a first year VED rate of £950, while motorists buying the least-polluting new models will not have to pay VED at all for the first year.
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