A million odd gas customers have been overcharged
Industry body Energy UK believe customers could have been overcharged by as much as 25p for each top-up. According to them, around 1.5 million meters haven't been working correctly for as long as seven years, as the meters were not properly calibrated to measure the cost of the gas being used.
In the worst cases, some customers may have been rinsed for as much as £110 extra.
"We apologise unreservedly to customers," said Lawrence Slade, the chief operating officer of Energy UK. "We have acted quickly, and we want those affected to get their money back as soon as possible," he told the BBC.
Gas customers will be refunded by their energy dealers, and their cards will be updated when they next need a top-up. British Gas, have already said more than 700,000 of its customers may have been overcharged.
Regulator Ofgem has called for a timetable for refunds and repairs, and it is thought that refunds will go out before Christmas.
"That overcharging has been going on for seven years shows the second-class service prepayment customers get," said Gillian Guy, Citizens Advice chief executive, adding: "Prepayment meter customers are already paying higher charges than direct debit customers, so this is adding insult to injury."