The AA is meeting Treasury ministers to argue that April's 2p rise in fuel duty should not go ahead.
The meeting comes as the latest AA figures showed the price of petrol at the pumps has fallen slightly in the last four weeks.
Between mid-February and mid-March the average UK petrol price fell from 90.88p to 90.56p. But overall in 2009 so far average prices have risen 3.41p.
In the last four weeks, three of the four main supermarkets have raised their average petrol prices while most non-supermarket retailers have lowered theirs.
Supermarkets remain broadly 1.4p a litre cheaper than the other retailers, although the price gap in many towns is extremely tight.
The cheapest petrol at present - at 90.2p a litre on average - is to be found in north west England and in Yorkshire and Humberside. Northern Ireland (91.6p) has the most expensive petrol.
AA president Edmund King said: "On April 1, if the Government goes ahead with its fuel duty hike, it will be conveniently forgetting that drivers also face the threat of severe financial hardship from the credit crunch. "On a wider scale, discussions the AA had with fellow European motoring clubs last summer on soaring fuel prices has led to correspondence with the EU's competition commissioner. The EU has now launched a probe of spot and wholesale fuel prices on the continent, which will be welcomed by UK drivers.
"Many still can't understand why, even with a 30 per cent loss in the value of the pound against the dollar, petrol is 90p a litre with oil at 45 dollars a barrel. In March 2007, the last time UK petrol cost 90p a litre, oil was priced at 68 dollars."