Price comparison sites allow customers to check whether they could be paying less for their gas and electricity.

Under the new Confidence Code, which goes live in March, the websites will have to show all tariffs available and make it clear which energy providers they have commission arrangements with.

"Comparison sites are a great place to start energy shopping, but customers need to feel confident that the sites are providing information they can trust," said Rachel Fletcher, a senior partner at regulator Ofgem, in an emailed statement.

Wholesale crude and gas prices in Europe have fallen in recent months due to a global supply glut, reducing some of the purchase costs the utilities incur and making the cost of energy a battleground for the country's politicians in the run-up to May's election.

Energy Secretary Ed Davey has encouraged people to look for better deals by switching energy providers.

The opposition Labour Party said it would try to introduce a law to give the regulator the power to force firms to cut prices in response to falls in wholesale costs.

Three of Britain's energy providers, Centrica (>> Centrica PLC), E.ON (>> E.ON SE) and Scottish Power, owned by Spain's Iberdrola (>> Iberdrola SA), have announced price cuts in the past two weeks.

That has put pressure on the remaining members of the 'Big Six' suppliers, EDF Energy (>> EDF), SSE (>> SSE PLC) and RWE npower (>> RWE AG), to do the same.

(Reporting by Susanna Twidale; Editing by John Stonestreet)

Stocks treated in this article : EDF, Iberdrola SA, RWE AG, E.ON SE, SSE PLC, Centrica PLC