A consumer organisation is launching a new campaign to get more energy customers to switch to cheaper tariffs by enabling them to group together in numbers to secure the best possible price for gas and electricity.
It explained how interested consumers will be asked to sign up by March 31 and then energy companies will be invited to submit deals and take part in a reverse auction.
The winning deal will then be offered to everyone who signed up and Which? will then handle the switching process.
Executive director Richard Lloyd said: "Thousands of people tell us that they want a much better, affordable energy deal. It's a £4 billion free kick for the energy companies if so many of us stick with their more expensive tariffs.
"The government, regulator and energy companies have failed to move quickly enough to improve things for consumers when so many are struggling to pay their bills.
"That's why we decided to launch The Big Switch. This is a completely new way to buy energy as a group. The bigger the group, the stronger our bargaining power will be."
The Big Switch is planned to take place during a single day as a reverse auction, which means energy companies will be invited to submit their lowest price per kilowatt of electricity and cubic meter of gas.
Which? said that once a deal has been secured, those who have signed up will be notified by either email or text message and they can then choose whether or not to accept it.
There will be no commitment or obligation to sign up with the new supplier.
Which? says UK consumers are collectively paying £4.1 billion a year more than they need to by not switching their energy tariff to the cheapest deal.
The organisers of The Big Switch are taking the campaign across the UK with a series of regional events in Reading, Glasgow, Manchester, Birmingham and Cardiff throughout February and March.
Almost 100,000 people have signed a 38 Degrees petition calling for a fairer deal on energy prices.
David Babbs, executive director of 38 Degrees, said: "We're all sick of gas and electricity companies ripping us off. If thousands of customers band together, we'll have the bargaining power to do something about it.
"The big energy companies act like they're untouchable, but this people-powered campaign can turn the tables and bring down prices for everyone."
Caroline Flint MP, Labour's shadow energy secretary, said: "This is a simple but potentially trailblazing way to help bring down
soaring energy bills. Even if this Government won’t stand up to powerful vested interests in the energy industry.
"I’m confident the British public will. When people come together, they’ll have more power to negotiate cheaper energy bills with the big energy companies."