The energy regulator, Ofgem, has been taken to task for resisting calls to investigate gas companies that have not passed on recent price reductions in the cost of gas.

The wholesale price of gas has halved since June last year, yet only two of the big six energy companies have cut their prices, and millions of people have not seen any reduction in their bills.

Consumer body Energywatch said that “millions of customers have been left out in the cold” by the energy companies’ refusal to cut their bills. “It’s indicative of a sleepy industry where they don’t feel they have to respond,” said Allan Asher, chief executive.

British Gas and Scottish and Southern Energy are the two companies that have cut prices, but Energywatch pointed out that the 17% British Gas price cuts are much less than the fall in wholesale prices and the 95% price increases of recent years.

Alistair Buchanan, chief executive of Ofgem, told the BBC: “Should Ofgem feel that companies are keeping jam on their fingers, we will instigate a thorough review.

“We have hard Competition Act powers… we can penalise them 10% of their revenues.”

But consumer Matt Higgins said: “The ordinary person is being taken to the cleaners yet again by the energy companies and my gas bills have not gone down a penny despite the reduced cost of wholesale gas. It’s a typical rip-off in my view.”