The prime minister’s troubles are worsening after a recent poll found that two-thirds of motorists said they will vote for a different government if the price of fuel rises to between 125 and 149p per litre.

The average price of diesel has already exceeded that level, while the price of petrol has passed it in some areas.

In the same poll almost half of the 18,500 respondents believe that the Government is most responsible for the rise in fuel prices.

The results are taken from an AA Populus panel poll – the biggest dedicated motoring panel in the UK – and indicate that cost is the major consideration, whether it is the cost of fuel or public transport.

However, the results show that there is little comprehension among UK motorists for the cause of the recent rises, or that they are occurring at a more rapid rate across the EU.

Almost half of respondents said that Mr Brown’s Government is most responsible for the rise in fuel prices, with 22% blaming oil producing countries and 20% blaming oil companies.

However, none blamed speculators, who have been widely criticised for being responsible for much of the recent price rises.

"These results suggest that motorists have little faith in politicians to deliver motoring-friendly policies,” said Edmund King AA president.

“Despite massive increases in the global cost of oil, motorists still blame the Government.

"Two thirds of motorists indicate that if fuel costs continue to rise to between 125p – 149p per litre then they will vote with their wheels against the Government.

"The Chancellor needs to act now to alleviate the fears of motorists.

"He should immediately abandon the threatened 2p increase in duty, set up a fuel price regulator and examine innovative ways of stabilising prices."