Millions of people pay too much for their electricity because they have not changed their supplier, says a report published today.

The report from the Commons Public Accounts Committee said six million people had saved £140 million a year by changing suppliers since competition was introduced just over three years ago.

But 19 million customers have not switched even though they could cut their bills by an average of 13%, saving a total of up to £670m a year.

The report criticised electricity companies for making it too difficult for consumers to switch suppliers.

The committee called on the industry's regulator, Ofgem, to force companies to make contracts less confusing for customers and to make it easier for people to compare the range of services on offer.

Consumers' groups backed the committee's demands for better information for customers.

A spokesman for the Consumers' Association said: "We need better transparency for consumers.

"At the moment they don't even bother to shop around because it's all too complicated."