The latest figures from the RAC and data firm Experian show the average price of a litre of petrol climbed to a record 185p on Sunday, while diesel hit 191.03p on Saturday before falling back to 190.9p on Sunday.
That is a 7p per litre increase for petrol and a 5.9p per litre rise for diesel in the space of a week.
The RAC says that the Treasury is now pulling in £46 in tax on a full-tank fill-up for an average family car and has urged the Government to take action now to ease pressure on drivers.
Based on an average 55-litre tank a petrol car now costs £101.77 to fill, while a diesel car costs £105.01.
RAC fuel spokesperson Simon Williams said: “The speed and scale of the increase is staggering, with unleaded going up 7p in a week and diesel by nearly 6p. This must surely put more pressure on the Government to take action to ensure drivers don’t endure a summer of discontent at the pumps.
“We hope the Government’s persistent talk about the importance of retailers passing on March’s 5p duty cut fully is a precursor to an announcement of a deeper cut this week. If that’s the case, it’s very welcome, albeit overdue as the 5p cut has been well and truly overtaken by events on the wholesale market since then.”
The Government has said that if the inquiry by the Competition and Markets Authority finds any wrongdoing, retailers could be “named and shamed”.
Fuel duty was cut from 57.95p per litre to 52.95p in March but since then wholesale costs and the price at the pumps have soared to all-time highs.
However, the AA has said that price rises “should be grinding to a halt” by the end of the week as wholesale fuel prices have fallen since the start of the month.
AA fuel spokesman Luke Bosdet said: “If they continue to go up substantially afterwards, we will be intrigued to hear what excuses the fuel trade has this time.
“If prices keep going up, they will give the Government further justification in its call to the Competition and Markets Authority (CMA) for an investigation.