The price of petrol is rising at the highest rate for 10 years.
Average prices between mid-December and the middle of this month increased from 122.14p per litre to a new record of 128.27p, the AA said.
The previous highest monthly petrol price rise in the last decade was the 5.6p-a-litre increase between May and June 2008.
Diesel went up from an average of 126.19p a litre in mid-December to 132.75p a litre in mid-January.
This 6.56p increase in diesel was just short of the highest previous-decade monthly increase of 6.8p a litre set in July 2008.
The AA said the 0.76p-a-litre increase in fuel duty at the beginning of this month and the VAT rise to 20%, adding around 2.5p more to the pump price, accounted for the lion's share of the latest increases.
An increase of around 5% in wholesale costs, driven by oil prices surging past 90 dollars a barrel, had ensured that every day was a record for petrol prices since December 10.
Compared to a year ago, petrol now costs 16.3p a litre more and diesel 18.98p a litre more. Filling a typical 50-litre fuel tank has risen £8.15 for petrol and £9.49 for diesel. For a two-car family, the monthly cost of petrol has increased by £34.61.
Following Government figures showing a 3.4% fall in petrol sales in the period July-September 2010 compared to the same period in 2009, a comparison of retail petrol sales between January and September 2010 with the same period in 2007 showed a 2.22 billion litre, or 12.8%, decline. With sales for petrol and diesel combined, UK retailers in the first nine months of 2010 sold 1.27 billion fewer litres of fuel compared to the boom time in 2007.
At present, the cheapest petrol is to be found in Yorkshire and Humberside (averaging 127.3p a litre), while the dearest is in Northern Ireland (129.1p).