The writer and broadcaster Victoria Coren Mitchell has indicated she may take legal action after claiming that her energy provider, Ovo Energy, wrongly pocketed thousands of pounds “that they were not owed”.

She is the most high-profile Ovo customer yet to apparently be on the receiving end of incorrect bills. Her case prompted the consumer group Which? to call for “the worst performers” in the energy sector, which it said included Ovo, to take urgent action to improve their customer service.

Scores of people on X shared their experiences with energy companies after Coren Mitchell told her 700,000 followers on the site that she had “reached the end of the road” with Ovo, which she claimed was “the most terrible service provider I’ve ever encountered … Nothing but legal action will do for them now”.

She claimed Ovo had “taken thousands of pounds that they were not owed” and the company had “driven me personally to despair”.

However, after some media reports that the energy company had taken the money from her bank account, she later clarified the situation, saying: “Ovo didn’t take money directly from my bank account. They sent big, incorrect bills, which I kept (protestingly) paying, and once I found the error, it proved impossible to put right.”

She said she was now in touch with a complaints person at Ovo, “who seems properly reachable, but I think we know why. I’m grateful, but I wish they’d offered the same service when I was an ‘ordinary customer’ under my anonymous married name”.

In response to her case, an Ovo spokesperson did not directly address the issues she raised but said the company was “always striving to provide the best possible experience for all our customers”.

“Our teams work extremely hard to provide help and support, and will continue to review lessons learned.”

Utilities customers are already struggling with bills that have soared, but energy firms have in some cases been adding insult to injury with mistakes and poor customer service. Incorrect billing, faulty smart meters and unpaid credit have left some households thousands of pounds out of pocket.

In November 2022, the Guardian reported that some Ovo customers were left shocked when they received bills of up to £49,000 because of data errors that led to overinflated energy projections.

At the time, the company admitted that meter-reading errors had affected some customers and blamed problems with some accounts that were transferred to Ovo after it bought SSE’s retail division in 2020.

In 2020, Ovo Energy agreed to pay £8.9m after the energy watchdog Ofgem uncovered a series of problems including wrongly billing more than 500,000 customers for almost three years.

However, reports of billing problems at the company have continued: the Guardian reported on a case in February this year.

Which? said customer service at some firms had hit “rock bottom” levels.

Rocio Concha, Which?’s director of policy and advocacy, said: “Nobody should have to put up with poor customer service, but sadly Victoria Coren Mitchell’s experience is all too typical. That’s why Which? will be campaigning for urgent customer service improvements from the worst performers – including Ovo – in key sectors.”

Coren Mitchell is not the only high-profile figure to take to X to complain about huge energy bills. Last December, the artist Grayson Perry said his EDF electricity bill had leapt from £300 a month to £39,000.

That prompted the journalist and broadcaster Jon Sopel – another EDF customer – to reply that a similar thing had happened to him, posting: “They wanted to raise ours from £152 to £18k.”

EDF suggested that incorrect meter readings recorded on its system might be to blame, adding: “We have robust interventions in place to ensure that any large increases in customers’ direct debits are verified through a human check and in almost all such cases, system errors are rectified and prevented, without customers being impacted.”