Motorists are now paying 142.99p for a litre of diesel, or £6.50 per gallon, on average, new figures have shown.
A report by the AA found the figure was up year-on-year from 122.83p.
Findings revealed that the average cost of petrol reached 137.24p a litre, or £6.24 a gallon, compared with the 121.43p a litre figure recorded a year ago.
According to the AA report, motorists are now paying nearly £8 more year-on-year to fill a typical 50-litre tank with petrol, while it is more than £10 more expensive to fill it up with diesel.
A two-car family was now having to spend £33.57 more a month for petrol than a year ago - highlighting that motorists will be looking for competitive car insurance quotes to compensate for the rise in expenditure.
The report found that the extra cost of filling an 80-litre diesel tank in a commercial van was £16.13.
© Press Association 2011