Shadow chancellor Ed Balls said the Prime Minister's actions in Brussels this week were "catastrophe for Britain and the British national interest."
"We won't be influential in the world, unless we are influential in Europe," he told BBC One's The Andrew Marr Show.
"I've never seen a negotiation so cack-handed," Mr Balls said about David Cameron's failure to stop the appointment of Jean-Claude Juncker as the new head of the European Commission.
Mr Balls said about the Prime Minister: "He's weak, he's lost control, he's on the back foot, Britain is suffering. I think it's catastrophic for Britain."
It should be no surprise that David Cameron failed to stop such a long-standing EU figure being nominated as European Commission president.
The PM's friends in Europe are bewildered that he would rather go down in flames than try for the best deal possible in the circumstances.
David Cameron is cruising for Euro-bruising over the election of Jean-Claude Jucker