Petrol debt recovery firm, Forecourt Eye, said staff were dealing with “very combative attitudes” from customers.

Soaring oil prices have pushed up the cost of petrol and diesel.  It now costs more than £100 to fill the average car.

Nick Fisher, chief executive of Forecourt Eye, said petrol station staff were being confronted by customers talking about being “ripped off” and asking questions like “how do you expect me to pay?”

He said customers were “becoming frustrated” at the high prices because they had remained high and kept creeping higher.

Many petrol stations rely on additional incomes made from sales of groceries, bakery items and coffee, he said.

But shoppers will not buy other products from a store where they feel they are being overcharged, he added.

Darren Briggs, chief executive of the Ascona Group said there had been a rise in the number of people who are driving off without paying for their petrol, which he linked to cost of living pressures.

The Petrol Retailers Association (PRA) said that petrol theft has continued to rise across the country.

Drive off incidents, where a motorist fills up and makes no attempt to pay before leaving, have increased by 61% so far this year, compared with the same period in 2021, according to figures from Forecourt Eye.

Mr Fisher said this was putting pressure on margins, and if the current rate of drive-offs continued it would cost businesses £25 million in lost fuel sales over a year.

Forecourt Eye digitally traces and tracks non-payers at more than 1,000 petrol stations and its new clients have doubled in the last two months due to the rise in non-payers, he said.

Mr Briggs from Ascona Group said petrol stations were often not making enough to recoup costs.

He said other pressures on margins included a reduction in how much fuel was being sold, as customers tried to save money – with the volume of sales at some sites only at 80% of normal levels.

Mr Briggs said it could cost up to £25,000 per month to run a petrol station, covering costs such as wages, utility bills, maintenance, repairs. He said money lost by non-payment was another financial blow.

Business Secretary Kwasi Kwarteng told petrol bosses the competition regulator is monitoring the situation.

However, the Petrol Retailers Association said margins were “often not enough to cover operating costs”.

Chancellor Rishi Sunak implemented the 5p per litre cut in fuel duty in March to reduce the price of fuel for motorists.

In a letter to the industry, the business secretary said the public was “rightly expressing concern about the pace of the increase in prices at the forecourt”.

He said people were frustrated that the fuel duty cut “does not appear to have been passed through to forecourt prices in any visible or meaningful way”.

“It is also unacceptable that different locations even within the same retail chain have widely different prices,” he wrote.

Mr Kwarteng said his officials recently engaged the Competition and Markets Authority about the issue, as a result of “perceived intransigence to date”.

“I have been reassured that they will not hesitate to use their powers to act against petrol stations if there is evidence that they are infringing competition or consumer law,” he said.

UK diesel prices rose to a record of just over £1.80 a litre on Monday, the RAC said.

After the previous record of £1.79 in March following the Russian invasion of Ukraine, prices dipped but have risen again in recent weeks.

The RAC said petrol prices went up by nearly 3p a litre since the start of May and were £1.66 a litre on average.

It said retailers are taking an average profit of 2p per litre more than before the chancellor’s 5p duty cut.

But Gordon Balmer, executive director of the Petrol Retailers Association, which represents independent forecourts, said comparing pump prices against wholesale prices “only gives a partial picture”.

Once “additional expenses” such as storage and delivery costs are taken into account alongside the “volatility of product prices”, retailers’ margins are “often not enough to cover operating costs”, he said.

He added that if the government wanted to lower pump prices, it should reduce fuel duty by more than 5p.

“5p per litre did not represent a substantial enough cut to ease the burden of rising prices on motorists,” he said.

“While the chancellor was announcing it, oil prices rose and effectively cancelled out the reduction. In addition to this, sales volumes of petrol and diesel are still not back to their pre-pandemic levels.

“Supermarkets and independent fuel retailers are competing vigorously with each other on the thinnest of margins.”

The row follows a warning that supermarkets have also not passed on the fuel duty cut amid falls in wholesale fuel prices.

The RAC motoring group does not believe the top four supermarkets – Asda, Morrisons, Sainsbury’s and Tesco – are doing enough to help customers cut their fuel bills.

RAC fuel spokesman Simon Williams said: “Despite operating just a fifth of petrol stations in the UK, the big supermarkets are responsible for around half of all fuel sales so how they choose to price petrol and diesel has a huge impact on what drivers end up paying.”

He added: “When wholesale fuel prices fall dramatically it can be enormously frustrating for drivers when pump prices don’t start coming down. It normally takes one retailer to effectively ‘fire the starting gun’ and cut its prices in order for others to follow.

“We know that the biggest retailers tend to be reluctant to reflect falling wholesale prices at the pumps day-to-day, yet they seem to pass on increases quickly when wholesale prices are rising. This can often be to the detriment of drivers.”

A Sainsbury’s spokesperson said: “We understand that the cost of living is a real challenge for many households and we are committed to helping our customers as much as we can.

“We lowered prices the day the chancellor announced fuel cuts so that our customers could benefit as soon as possible.”

Morrisons said it took the full 5p from its prices at 6pm on the day of the chancellor’s announcement.