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New Labour architect Peter Mandelson has warned that the party could appear to be going backwards if it sticks to leader Ed Miliband's pledge to freeze energy prices, the Guardian reported on Thursday.

He argued that Miliband's promise to freeze prices for two years if he wins power in 2015 meant that "perceptions of Labour policy are in danger of being taken backwards".

"At the business department I tried to move on from the conventional choice in industrial policy between state control and laissez-faire," he was reported as saying by the Guardian.

The former business secretary was one of the prime figures in making the party more pro-business before Tony Blair's election triumph in 1997.

Former Labour minister Digby Jones also weighed in, calling it "a return to ideological tribal socialism".

Miliband made the promise during a rousing address praised by delegates and his trade union supporters Labour party conference in Brighton.

He said the policy would "benefit millions of families and millions of businesses" but energy firms warned it could cause black-outs.