Motorists already facing rising pump prices will be hit by another Government fuel-duty increase tomorrow.

Despite intense lobbying to get it to reverse its decision, the Government is pressing ahead with a planned 2p a litre rise in fuel duty.

With VAT included, the rise will actually be 2.3p at a time when the average price of petrol has risen to around 105p a litre.

Motoring organisations fear that the 2.3p a litre increase could soon become a 5p rise as oil prices worldwide increase.

The RAC said that a 5p increase would mean the average two-car family spending an extra £120 a year on petrol.

The duty rise will be the third in nine months following rises in April and December. Petrol prices at the start of 2009 were roughly 85p a litre but could now reach 110p a litre within weeks.

This rise of 25p over the past nine months equates to roughly £600 more a year for the average two-car family.

RAC motoring strategist Adrian Tink said: “This third fuel-duty hike is unacceptable.

Since the start of 2009, Britain's motorists have seen a 23% rise in pump prices, meaning an extra £11 per tank for the average car.”The Chancellor seems to regard Britain's 30 million motorists as a soft target for tax and with this latest rise he risks alienating them even further. The Government needs to appreciate the impact such taxes have on cash-strapped families and, at the very least, provide people with some clarity over where this money is being spent.

"Mr Tink said that it was planned to raise fuel duty yet again in April. He went on: “With VAT also returning to 17.5% it could be a very long winter for motorists.”

This year's annual RAC report on motoring found that drivers continue to oppose further rises in fuel duty unless they see a demonstrable improvement in the service they receive in return.

As many as 80% of motorists surveyed believed that the current level of tax on motorists was too high in relation to the service they received on the country's roads.

Also, 83% did not believe that the motoring taxes they pay were sufficiently re-invested into the right areas.