Petrol prices shot up by by 5.44p a litre in April, adding £3 to the cost of filling up an average family car.
This is the second worst monthly rise since 2000.
A litre of unleaded rose by more than 5p in April from 122.62p to 128.06p, according to RAC Fuel Watch data.
The RAC says this was a result of retailers passing on wholesale price increases driven by a 5% jump in the cost of a barrel of oil.
Diesel also increased by 3p a litre from 130.70p to 133.70p.
This is the third consecutive month of price rises, meaning unleaded has gone up 8.5p a litre from 119.54p to 128.06p since the beginning of February.
The cost of filling an average 55-litre family car has gone up by £3 to £70.43 and for diesel by £1.65 to £73.54.
RAC fuel spokesman Simon Williams says: “Despite the good weather April turned out to be one of the bleakest months ever for drivers with the second biggest monthly rise in the price of petrol for nearly 20 years.
“RAC Fuel Watch data shows the price of unleaded rose every single day from the end of March for three and half weeks until 24 April, which is the longest run of daily price rises since May last year when unleaded increased 6p a litre setting a new monthly price rise record dating back to 2000.
“The bad news for drivers is that a tank of petrol now costs £3 more than it did at the start of April. This will have a damaging effect on household budgets across the country and will inevitably mean there will be less money available for non-essential spending.”
The country’s four big supermarket fuel retailers – Asda, Morrisons, Tesco and Sainsbury – all increased their petrol prices above the UK average.
Motorway petrol went up 3.6p from an average of 141.93p to 145.53p with diesel increasing 2.79p from 151.27p to 154.06p.
The RAC says retailers have been using the cheaper wholesale cost of diesel to subsidise petrol pump prices a new monthly price rise record would have been set.
Mr Williams adds: “Diesel drivers have much to be aggrieved about as the fuel not only suffered a 3p a litre hike in price, its pump price was 6p higher than petrol on average in April – despite the fact its wholesale cost was very similar to that of petrol.”