Millions of people could have their gas and electricity prices cut under a watchdog's proposal.
The Competition and Markets Authority (CMA) has suggested energy prices should be temporarily capped for four million households on pre-payment meters.
They will see £300 million slashed off their bills in total each year - around £80 to £90 each on average - under the regulator's plans to protect them with a price cap until 2020.
Energy suppliers will also be forced to open up consumer databases to allow rivals to offer those on standard variable rate tariffs better deals.
The CMA said British households could have been overpaying by around £1.7 billion a year.
They added that the Big Six providers had been taking existing customers - 70 per cent of whom are stuck on standard variable rate deals - for granted.
Its reported stated it wants to set a temporary price cap for low income and vulnerable customers who have pre-payment meters.
The proposals are intended to reform the energy market and increase competition, in order to help consumers save money.
Additional reporting by agencies
