No magic wand to curb energy prices, warns Nick Clegg - Telegraph.co.uk

EDF Energy, npower and Scottish Power will offer customers fixed-price energy deals, directly linking the deals to the Labour pledge. The deals would be slightly higher than current tariffs, although consumers would stand to benefit if prices rose significantly before 2017.

Caroline Flint, the shadow business secretary, said: "This shows that all the warnings about blackouts were nothing more than scaremongering." Conservative sources said the deals proved the pledge was a "gimmick", as customers could avoid price rises without legislation.

A dispute has developed in the Labour ranks over the pledge, with a public disagreement between Miss Flint and Lord Mandelson. Centrica and SSE, two of Britain's biggest energy companies, lost almost £2?billion in value as their share prices fell after Mr Miliband's announcement. Neil Woodford, Centrica's biggest shareholder, described the plan as "economic vandalism" and said energy companies should pull out of Britain.

Mr Clegg echoed that warning on Thursday, saying it was "not fair on the British people to somehow pretend that all you need to do is wave a legislative pen" to cut the price of power. "Everybody wants to do something about high energy bills," he said. "But I think they want to see politicians come up with real, serious answers — not wholly incredible proposals."

He called for Britain to invest in renewable energy, nuclear power and fracking, but warned that it would take "some years" before prices begin to fall.

Mr Miliband announced in his speech to the Labour Party conference that he planned to pass emergency legislation forbidding energy companies from increasing domestic prices until 2017.

Lord Mandelson, the former business secretary, said it risked making the party look like it was "going backwards".

Miss Flint accused the peer of being influenced by financial interests. He runs Global Counsel, a business advice firm that lists the energy industry among its expertise. She said: "I know Lord Mandelson has financial interests in energy companies. I don't know if he's just speaking to them." Lord Mandelson's firm replied: "Global Counsel does not provide services to any of the energy companies who would be affected by Labour's new policy."