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."
Ed Balls said policy chief Jon Cruddas was "excited" by the party's agenda despite him claiming that Labour was stopping bold reforms in favour of "cynical nuggets of policy."
The shadow chancellor told the BBC's Andrew Marr show: "I talked to Jon a couple of days ago and he's not frustrated, he's excited about his policy agenda.
"He's frustrated by the way in which one report of 250 pages gets reduced down to one headline."
He added: "Jon Cruddas, with me and Ed and others, has been working for years on big reforms, they're going to come out in the next few months, people will see the policy review he has led has been a big deal."
Shadow chancellor Ed Balls has been issued with a summons in connection with a car crash.
The MP is facing allegations that he failed to stop after driving into another car in his constituency in April.
His office said he would not be contesting the charge, with the case due to be heard at Leeds Magistrates Court on August 5.
Mr Balls previously said that he had "no idea" he had caused any damage until he was contacted by police.
Labour's shadow chancellor Ed Balls said:
George Osborne is still failing to tackle the root cause of the housing crisis which is that we are not building enough homes to match rising demand.
Over the last few years Labour has repeatedly called for action on housing supply, but the Chancellor has failed to act.
Under this government housebuilding has reached the lowest peacetime levels since the 1920s.
You can't deal with the cost-of-living crisis and create a strong and balanced recovery without building more homes.
Shadow Chancellor Ed Balls has been told by police that he faces being charged for failing to stop after driving into another car.
Mr Balls reiterated on his blog that he "had no idea" he had damaged another vehicle during the incident in Morley, West Yorkshire, last month.
"I'd been turning our car round in a tight spot in the narrow private drive beside the Labour rooms in Morley where I park all the time," he wrote.
"Another car was parked close by and I was aware the two bumpers touched. But I had no idea any damage had been done until the police got in touch a week later."
He confirmed that, "of course I will be accepting the charge" and suggested he expected to be punished with penalty points on his licence.
A West Yorkshire Police spokesman said they were still consulting with prosecutors and no formal decision had been taken to proceed.
Police have launched an investigation into an incident in which shadow chancellor Ed Balls drove away after colliding with a parked car without telling the owner.
The Labour MP was involved in the collision in his Morley and Outwood constituency on April 5th.
Mr Balls issued a statement saying he had not realised the other car had been damaged but has now apologised to the driver.
"Until I was contacted the following Wednesday, I had no awareness at all that there had been any damage to the other car. As soon as I was made aware of what had happened, I took full responsibility for any damage caused," Mr Balls said.
"I have written to the owner of the other car to say I was terribly sorry and to reimburse the owner concerned for the necessary repair," he added.
Communities Secretary Eric Pickles has hit back at Ed Balls after the shadow chancellor suggested he had fallen asleep during today's Budget speech.
Mr Balls had told a briefing of lobby journalists:
"Eric Pickles fell asleep for a quite extended period of time and Ed [Miliband] and I were worried because, you never know, there might have been some big cut in local government spending coming which he didn't know about so we just politely suggested to Vince Cable that he should wake him up."
In a Twitter reply to the Daily Mail's Tim Shipman, Mr Pickles witheringly dismissed Mr Balls' claims.
Ed Balls has revealed the Labour front bench spent much of the Budget speech urging Vince Cable to wake up Eric Pickles.
Ed Balls has called on George Osborne to "do the right thing" in tomorrow's Budget and help lower and middle-income families.
The shadow chancellor said "most people are worse off" now than when Mr Osborne became Chancellor in May 2010 and claimed the Government had raised taxes 24 times:
Manchester United star Wayne Rooney's reported £300,000 a week should not be controlled as his talent attracts the high salary, shadow chancellor Ed Balls has suggested.
Mr Balls said in the footballer's case it was perhaps "genuinely the talent getting the pay" as there is "only one Wayne Rooney" who could go anywhere in the world.
Mr Balls made the remarks after he was questioned about Business Secretary Vince Cable's comments in the Observer that he did not understand "why people need a million quid a year".
He told BBC Radio 5 Live's Pienaar's Politics: "I think in some parts of our economy - when it's not a great idea or when it's not the talent of Wayne Rooney - then you do think to yourself these massive multimillion-pound salaries, it feels like a bit of a Ponzi scheme."
Shadow chancellor Ed Balls has ruled out a reversal of the rise in VAT in an interview on the BBC's Andrew Marr Show, adding that he is "daunted" by the size of the deficit.
In 2012, Balls called for a temporary cut in VAT in an effort to boost the economy, but says the public finances would not allow such a measure after the next election.
Mr Balls added that the breadth of the "cost of living crisis" meant it was unlikely Labour would restore child benefit for higher earners, even though he would "like to".