Ed Miliband has accused David Cameron of failing to secure a plan for growth at the recent G8 summit in the United States because he was "on the wrong side of the economic argument".
The Labour leader expressed surprise that Cameron had claimed to be "best buddies" with Socialist French president Francois Hollande seeing as he had openly backed his opponent, former leader Nicolas Sarkozy.
Miliband said the Foreign Office had been so disturbed by Cameron's decision to back Sarkozy that it had been actively briefing against him.
"They said we put all the chips on one card and it turned out not to be the ace, it was an error of judgment and not what was advised," Miliband told MPs.
He said diplomats had said the prime minister "has a habit of shooting from the hip".
Speaking in the House of Commons on Wednesday, Miliband said the summit had been a failure because the international community was divided about how to rescue the global economy.
"It's divided between those who believe we must have decisive shift towards growth; Obama and now Hollande.
"And those who believe we need more of the same, the German chancellor and this prime minister."
Miliband added: "He has been the high priest of austerity, he has been telling the world for two years that austerity is the answer. Now of course the recongition has dawned that it isn't working."
"Thats why he is desperately scrabbling around to say president Hollande is his great friend."
"What did the prime minister acutally achive at this summit? We do know some of things he did, he watched the football, nice pictures, he went to he gym, he even squeezed in some sightseeing, the only thing there isn't a photo of is him making a difference to the world economy."
But Cameron said that Miliband did not offer a plan of his own and chose to hit back at the Labour leader's jibe about his support for Sarkozy.
"It is a good joke about Sarkozy, we all have our faults but i'd rather have a reputation for being loyal to my friends than one for knifing my brother."
Cameron said Hollande had said the national debt was "the enemy of France" and Miliband would be wise to listen to that warning.
"If you look at what president Hollande is doing, he was asked how he would stimulate growth [he said] the means can not be extra public spending," Cameron said.
"No one, even the left wing party in Greece, backs his [Miliband's] idea of an extra £2bn of borrowing."
Cameron and fellow EU leaders meet in Brussels tonight under intense pressure to agree new economic growth plans ahead of a crucial Greek election vote.
With the vote being billed as a verdict on continued eurozone membership for Greece, markets are banking on the summit to lift the gloom.
The aim is to discuss jobs, growth, trade and boosting the EU single market, but officials in Brussels insist the "informal" meeting will reach no conclusions on Greece.