Ed Miliband today pledged to freeze gas and electricity prices if he becomes prime minister after the next election.
The Labour leader used his party conference speech in Brighton to claim that he was "standing up to the strong."
"The system is broken and we're going to fix it. If we win that election in 2015 the next Labour government will freeze gas and electricity prices until the start of 2017," he said.
"Your bills willl not rise. It will benefit millions of families and millions of businesses. That's what I mean by a government that fights for you. That's what I mean when I say Britain can do better than this."
He admitted that "the companies aren't going to like this," but insisted that he would prevent them from simply raising prices even more afterwards.
Speaking on the BBC, Labour's shadow energy secretary Caroline Flint said the party would pass legislation to "reset the market" in their first two years.
"We're talking about a freeze until January 2017 to give us time in government to get the reforms to the market through," she insisted.
Asked whether she expected energy companies to simply put up their prices before the election to compensate, she replied that it was a matter for the current government.
"I think the energy companies need to think very carefully about how unpopular they want to make themselves with the British public," she said, adding that "David Cameron is the prime minister, maybe he should do something about it".
Miliband also pledged to "break up the big six" energy companies so that their producing arms are separated from their energy supplying arms.
Labour sources say their policies could save families around £120 a year.
They admit that energy companies would be likely to take them to a judicial review but insist that any such attempt would fail.
The government quickly dismissed Miliband's plans, saying that they would lead to "lights going out".
"Labour's plan is a promise that won’t work," energy and climate change secretary Ed Davey said.
"When they tried to fix prices in California it resulted in an electricity crisis and widespread blackouts. We can’t risk the lights going out here too.
"Fixing prices in this way risks blackouts, jeopardises jobs and puts investment in clean, green technology in doubt."
The Labour leader spoke for over an hour without notes and received his best reception for a pledge to reverse what he called the "privatisation of the NHS".
"It's the same old story. We rescue the NHS, they wreck the NHS and then we have to rescue it all over again," he added to a long standing ovation.
He also pledged to build 200,000 new homes a year by the end of the next parliament and to extend votes to 16- and 17-year-olds.
Miliband's speech began as a new poll found that six in ten people do not believe that he comes across as an election winner.
The ComRes poll found that half the country believes Labour would have a better chance of winning the next election without him.
Miliband today responded to questions over his leadership by saying that he "relished" the debate over character.
"If they want to have a debate about leadership and character be my guest," he said, adding that "David Cameron was the prime minister who introcuced the bedroom tax. I will be the prime minister who repealed the bedroom tax."
The speech was well received by Labour MPs in the room. Hilary Benn told Politics.co.uk afterwards: "It was brilliant. Someone's just said to me if David Cameron was watching that he'll be thinking 'blimey'. He's completely up for the fight."