David Cameron has pledged to roll back “green charges” that add an average of £112 to energy bills, as he came under fire over Sir John Major’s call for a windfall tax on the excess profits of Britain’s big six energy companies.As Ed Miliband mocked the prime minister in the wake of Major’s call for state intervention on energy prices, Cameron announced an annual competition review to examine the cost of green regulations and the level of profits.The PM said: “I can tell the house today that we will be having a proper competition test carried out over the next year to get to the bottom of whether this market can be more competitive. I want more companies, I want better regulation, I want a better deal for consumers. But yes, we also need to roll back the green charges that he put in place as energy secretary.”The review, which will be carried out by the Office of Fair Trading and the new Competition and Markets Authority, is to be announced next week in the annual energy statement. The chancellor, George Osborne, is to announce any changes to levies in his autumn statement.Downing Street later said the prime minister was determined to roll back the costs of green levies. But government figures showed that the largest proportion of the £112 the charges add to the average bill were related to measures aimed specifically at less affluent people.