Labour leader Ed Miliband's plans for a 20-month freeze on energy prices have been sharply criticised by the head of an international economic watchdog.

Angel Gurria, secretary-general of the Organisation for Economic Co-operation and Development, said the freeze - which Labour has said it will implement if the party wins the next general election - would simply drive away investors.

"If you freeze the price of energy and the international prices of energy rise, it means there is going to be a very big difference to pay," Mr Guirra said in a televised interview.

"How are you going to get people to come in and invest to get their money back in 30 or 40 years' time when you are saying there is going to be a freeze?"