Thousands of British consumers are being denied the chance to find a less expensive energy firm because they are in debt to their current provider, it has been claimed.

According to MoneyExpert.com, around 726,000 people have missed a gas or electricity bill in the past six months and for many the resulting debt problems are causing significant financial headaches.

The price comparison firm has noted that energy firms tend to be unwilling to allow their indebted customers to switch suppliers, which leaves consumers with what on many cases is an uncompetitive gas or electricity tariff.

In addition, MoneyExpert.com is expecting to see household energy bills rise over the course of 2008, which could add to the debt problems many families are already facing.

"It’s inevitable that gas and electricity prices will rise again, so we anticipate large numbers of people to look to switch to the most competitive deals once that process begins," said Sean Gardner from MoneyExpert.com.

The Council of Mortgage Lenders recently urged Britons with debt problems to prioritse their arrears in order to pay them off more easily.