The National Housing Federation says customers who use pre-payment meters have overpaid the energy companies nearly half a billion pounds.

It's believed the high charges for using the meters were in breach of EU rules and there could be grounds for customers to claim the money back.

According to Government statistics customers on prepaid meters have been paying around seventeen per cent more than those who pay by other means.

Around twelve per cent of energy customers use pre-paid meters. Not all, but many of these, will be low income households that can least afford to pay higher prices.

Since 2006 until last year, energy suppliers charged these customers hundreds of millions of pounds more than they were allowed to under EU rules.

In an interview with the BBC, Paul Rees from the National Housing Federation said "It's very shocking that five energy companies would overcharge customers to the tune of £460 million and that they would do that in breach of EU rules. I think it's scandalous that Ofgem, the energy regulator, has failed to enforce the EU directives because it is there to protect the consumer."

The National Housing Federation is now raising the possibility that customers may take action to get this money back. While the energy regulator Ofgem admits customers on pre-paid meters were unjustifiably paying more, they have now forced energy companies to bring prices down within EU rules.

Garry Felgate from Energy Retail Association remarked: "What the regulator has actually said is that it does cost more to run the pre-payment meters, but as of the end of last year, they asked the energy companies to bring down the prices to normalise them and those prices have come down by £300 million overall on prepayment customers so they are now at a comparable price to everybody else."

The energy suppliers are remaining tight-lipped on the issue of paying money back. Haley says she would consider taking action to get it, but for now she just wants her pre-payment meter taken out.