Mr Miliband has said that drops in wholesale prices should result in price cuts being passed on "immediately" to consumers.
The ERA has stated there will "always be a time lag" between wholesale price drops having an effect on customers' bills as the gas being used today "may have been bought back in the summer or even earlier", when prices were at record highs.
It added: "However, in a competitive energy market all energy companies want to win your custom and will be looking to lower prices at the earliest possible opportunity and they have already made this clear."
Research by industry watchdog Consumer Focus found that people living in Plymouth pay the highest fuel bills in England, according to the Plymouth Herald.
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