Pressure on the Government to take action on fuel prices intensified after the average cost of petrol reached a new high.

The RAC said a further cut in duty this week would be “very welcome, albeit overdue”.

Figures from data firm Experian show the average price of a litre of petrol at UK forecourts climbed to a record 185.0p on Sunday.

That is an increase of 7.1p in just a week.

The average price of diesel was 190.9p per litre on Sunday.

A 5p per litre cut in fuel duty was implemented by the Treasury in March, but the Government has claimed the reduction is not being reflected in pump prices by all retailers.

The wholesale cost of fuel has soared since the measure was introduced.

RAC fuel spokesman Simon Williams described the “speed and scale” of the rise in fuel prices as “staggering”.

He went on: “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.”

Business Secretary Kwasi Kwarteng ordered an “urgent” investigation into petrol station operators over the weekend amid concerns some are pocketing the 5p cut.

In a letter to the Competition and Markets Authority (CMA), the Cabinet minister wrote that people were “rightly frustrated” that the reduction had not stopped prices from soaring.

The recent rise in petrol prices “should be grinding to a hat” by the end of the week due to a drop in wholesale prices since the start of the month, AA fuel price 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.

Mr Bosdet added that the “relentless surge” in wholesale and retail costs for diesel is “a nightmare” which will have a knock-on impact on delivery prices for goods and services.