Warnings that Britain could face blackouts if Labour enforces a freeze on gas and electricity prices were today dismissed as "scare stories" by Ed Miliband, as he compared the energy companies to banks resisting regulation ahead of the 2008 crash.
Mr Miliband wrote to the "Big Six" companies warning that they would face a consumer backlash if they fought his plans for a 20-month freeze following the next general election in May 2015.
His surprise announcement at the Labour conference in Brighton yesterday was greeted with horror by energy suppliers, with predictions that firms deprived of the power to set their own prices would be in danger of "economic ruin".
Shares in Centrica - British Gas's holding company - fell by 5.3% in trading over the course of the day, while shares in Swalec owner SSE fell 5.8%.
Centrica chairman Sir Roger Carr said: "We are all concerned about rising prices and the impact on consumers, but we also have a very real responsibility that we find supplies to make sure the lights stay on."
And Angela Knight, chief executive of trade body Energy UK, said that while the price freeze was "superficially attractive", it would "also freeze the money to build and renew power stations, freeze the jobs and livelihoods of the 600,000-plus people dependent on the energy industry and make the prospect of energy shortages a reality, pushing up the prices for everyone".
But Mr Miliband made clear he would not be moved by warnings that companies could scale back investment or pull out of the UK power market, or that the lights may go out as a result of the freeze.
In his letter, he told the Big Six: "You and I know that the public have lost faith in this market. There is a crisis of confidence.
"We face a stark choice. We can work together on the basis of this price freeze to make the market work in the future. Or you can reinforce in the public mind that you are part of the problem not the solution."
The Labour leader told the BBC: "We will have scare stories from the energy companies, like we had scare stories from the banks - threats, scare stories about regulation. I'm not going to tolerate that.
"The Conservative Party will support them, but I'm in a different place. I'm standing up for the British people."
Mr Miliband said he would not tolerate companies "colluding" to raise prices in the period before the election to offset the financial impact of the freeze, estimated to save the typical household £120 and an average business £1,800 between May 2015 and January 2017, at a cost to industry of £4.5 billion. He said Labour would support David Cameron if the Prime Minister implemented an immediate freeze.
However, the Labour leader said he believed the energy market to be "exceptional" because of flaws in the way regulation had worked since privatisation, and indicated that he was not planning similar action in other sectors dominated by a few suppliers, such as mobile phones and broadband.
The annual conference ended with the traditional chorus of the Red Flag, as deputy leader Harriet Harman told delegates: "The g eneral election is there for the taking... W hile we are in no doubt about the scale of our task, we all leave here determined to do whatever it takes to kick out this miserable coalition and fight for a Labour government."
After a week in which Mr Miliband unveiled plans for a hike in corporation tax, compulsory purchase of land being hoarded by developers and new requirements for employers to take on apprentices, Conservatives said that the Labour leader had revealed himself to be "Red Ed".
And CBI director-general John Cridland said the conference had delivered "a real setback for Labour's pro-enterprise credentials".
Mr Cridland told BBC2's Daily Politics: "I think business as a whole will say we look to the Labour Party to speak for all business, not to beat us up and then say it's speaking for small business, not large business. Speak for all business, Ed, and do it in a way which takes businesses with you.
"Government is there to set minimum standards. You begin interfering price and property and wages, as well as in tax, and you put business taxes up, how do you expect that to have a positive impact on wealth creation, job creation and more jobs on the high street?"
But Mr Miliband said that the action on energy prices was at the heart of the message about the "cost of living crisis" that he will take into the 2015 election
"What you've seen from Labour this week is a party standing up for ordinary families, not for the privileged few," he told Channel 4 News.
"The election question is this - Whose side is the Government going to be on? Are they going to make life easier for ordinary families, or just the privileged few? Will you tackle the cost of living crisis? That's what we will do in government."
Asked if he was bringing in a socialist agenda, Mr Miliband told the BBC: "It says on our party card 'democratic socialism' That was written by Tony Blair.
"What democratic socialism means today is an economy that works for all working people, and not just a few at the top. It means markets that work in the public interest. And it means responsibility all the way up in society, including the big energy companies.
"I think I'm standing where the British people stand. A country that works for them, not just a few people at the top of society."
Ramsay Dunning, general manager at Co-operative Energy said: "It's no surprise to see the Big Six objecting to Ed Miliband's pledge to freeze energy prices from 2015 until 2017. The British energy industry has been in the grip of a stranglehold by these companies for far too long.
"We believe it doesn't have to be this way and something has got to change to help energy customers all over the UK who are not only confused and deprived of any real choice but worryingly for many, unable to pay their energy bills."
Energy Secretary Ed Davey said: "Everyone wants to help with the cost of rising bills but we need to be sensible.
"Government price-fixing jeopardises investment in new power stations, making power cuts a real possibility.
"It also puts at risk Britain's transition to a clean, green, low carbon future.
"The best way to keep everyone's bills down is to help people to save energy, ensure fair tariffs and encourage competition. That is exactly what the Government is doing."