David Cameron and Ed Miliband traded blows in the Commons today over the Labour leader’s price freeze promise, as energy policy took centre stage in the first Prime Minister’s Questions since the party conferences.

Mr Miliband has promised to freeze energy prices for 20 months if Labour come to power in 2015.

The Prime Minister said: “Just 12 hours after making his pledge, he said he might not be able to fulfill it because of international wholesale gas prices.”

He added: “I know he’d like to live in some sort of Marxist universe where you can control all these things but he needs a basic lesson in economics.”

Miliband fired back saying the Prime Minister still hadn’t decided whether it was a good idea or not: “He is floundering around and he has no answer to Labour’s energy price freeze.”

He repeatedly pressed the Prime Minister to confirm that energy bills had risen by £300 under his rule adding: “He says he wants low prices but prices are going up on his watch. That is the reality.”

The Labour leader went on to accuse him of siding with suppliers: “Energy bills are rising and he supports the energy companies not the consumer. We have a prime minister who always stands up for the wrong people.”

In response, the Prime Minister said he would lower bills by tackling the causes of high of prices, describing Labour’s answer to the problem as “a gimmick that collapsed after 12 hours.”