A study released by the regulator reveals that 52 per cent of switchers leave their old account in credit, and several of the largest energy suppliers generally make no effort to repay the outstanding balance to former customers. This means that at least £153m is owed to former customers by the Big Six, with some customers owed over £160.

Ofgem has referred to these sums as “unacceptably large”, and demanded that suppliers recompense affected customers accordingly; as a result, Energy UK have launched the ‘My Energy Credit’ campaign, encouraging consumers to investigate whether they are owed money and how much.

According to Energy UK, to date, four in five claimants have successfully recouped credit owed, at an average of £88 each; a quarter have received more than £100. Some have retrieved as much as £300. The age of a claim is also immaterial; some have applied to switches made decades ago.

“Around three million have unclaimed credit balances. We want to reduce that number to zero,” said Lawrence Slade, chief executive of Energy UK. “We recognise that people lead busy lives – however, if you have switched or moved house, please do contact your old supplier to see how much ‘energy credit’ you might be owed.”

Readers who think they may be owed money by their former supplier should visit myenergycredit.com.