The independent watchdog Consumer Focus has accused the big six energy suppliers of failing to fully pass on recent wholesale price cuts.
They claim the public is being overcharged by more than £1.7bn.
All of the six main energy suppliers have cut their prices since the beginning of the year, typically by about ten per cent, but Consumer Focus claims that's not enough.
The consumer watchdog says that for the average customer, gas bills should be about £60 cheaper still and electricity bills should fall by another £14 a year. Consumer Focus says its research is based on figures from the energy regulator Ofgem and the falling price of crude oil which is now about $70 a barrel compared to $147 last July.
Audrey Gallacher, from Consumer Focus commented: " We hope companies will sit up and immediately reduce prices and if they don't, we would hope that the Government would step in and do some investigation into why there's this disparity."
But the energy companies say the report from Consumer Focus is misleading and they deny that their customers are being overcharged.
Garry Felgate, Energy Retail Association: "Energy companies have to hedge the purchasing of their gas and electricity. They do that quite simply so that we have the guarantee of supply of the gas and electricity that we need. We've just gone through one of the coldest winters and, unlike many other European countries, we've always had supply. That's because we've been buying ahead to guarantee that supply."
The energy companies also say that the amount of gas and electricity only accounts for about half of energy bills. The rest is used to pay for such things as transport and meeting carbon emissions targets and that those costs have risen sharply in recent years.