Ofgem said it is satisfied that electricity and gas companies are doing enough with regards prepayment meters and customers in debt.
However the news provider claims customers are being saddled with debt "out of the blue" when energy firms backdate bills after failing to update prepayment meter tariffs.
In an interview with the Post, Mr Cameron said: "This programme of back billing basically charging people extra for energy they have already consumed is quite wrong. Three out of the six big suppliers have stopped doing it."
"Ofgem needs to have a really good look at this and try to put a stop to it," he added.
In related news, E.ON is closing a call centre and cutting 450 jobs across the UK.
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