Energy suppliers are overcharging customers by almost £100 a year because they are failing to pass on price cuts, research has suggested.
Despite falling world oil prices, Britons are still paying more to heat and light their homes than last summer, with household electricity and gas bills averaging more than £1,200 a year.
The reduction in wholesale prices means gas bills could be slashed by up to 10% and electricity by 3.5%, leading to annual savings of £96.40, according to research published in The Daily Telegraph by the Consumer Focus watchdog.
By failing to pass on the full discounts to every household, power companies are estimated to be making an extra £2.2 billion, the newspaper said.
Robert Hammond, energy expert for Consumer Focus, which is publicly funded, said: "The fact that wholesale prices are at a three-year low adds further to the already heavy weight of evidence that greater energy price cuts are needed.
"These declining costs will contribute to energy firms paying less for gas and electricity. So, it is only right that these price cuts are passed on to consumers, many of whom are struggling to afford high energy bills.
"If the suppliers do not want to be accused of treating their customers unfairly they must make immediate price cuts."
Industry regulator Ofgem has given suppliers until next week to explain why they have not passed on lower wholesale electricity and gas prices to households.
Garry Felgate, chief executive of the Energy Retail Association, which represents suppliers, said power companies buy much of their energy in advance and the current price on wholesale markets does not reflect what they paid for their supplies.
