Investors could be put in financial danger if firms are forced to absorb wholesale price increases, said Angel Gurria, the organisation’s secretary-general.

Labour leader Ed Miliband has pledged to freeze energy bills for 20 months if his party wins the 2015 election, following public outcry after huge price rises.

Labour said the “big six” energy firms have been overcharging people.

Mr Gurria, head of the Organisation for Economic Co-operation and Development, said Labour’s policy could damage business.

“If you freeze the price of energy, and the international price of energy rises, it means there’s going to be a very big difference to pay,” he told the BBC.

“Who’s going to be paying the difference? Are you going to ask the investors?

“They’ll probably go bankrupt. How are you going to get people to come in and invest to get their money back in 30, 40 years’ time when you say there’s going to be a freeze?

“I think this is simply not consistent, not economically objective.”