Boris Johnson has issued a bizarre backing of Tory backbench demands for an EU referendum bill and attacked British workers and their 'sloth'.
The London Mayor has questioned why 'person for person' Germans are more productive than British employees and warned eurosceptics that quitting the EU would expose the fact that most of the country's problems were self-inflicted.
He also warned David Cameron he must make clear Britain is "ready to walk away" unless its relationship is fundamentally reformed.
"If we left the EU, we would end this sterile debate, and we would have to recognise that most of our problems are not caused by 'Bwussels', but by chronic British short-termism, inadequate management, sloth, low skills, a culture of easy gratification and underinvestment in both human and physical capital and infrastructure," he said in his Daily Telegraph column.
"Why are we still, person for person, so much less productive than the Germans? That is now a question more than a century old, and the answer is nothing to do with the EU. In or out of the EU, we must have a clear vision of how we are going to be competitive in a global economy."
Mr Johnson's intervention in the fraught Conservative debate over the UK's future in Europe came after two senior cabinet ministers publicly declared that they would vote No if the present relationship was put to a vote.
He pledged his "full support" to the Prime Minister's strategy of seeking a new pared-down deal to put to the country in an in/out referendum by 2017 if the Tories win the next general election.
But he said he wanted to see "legislation now to make sure that referendum goes ahead".
Up to 100 Tory MPs are tipped later this week to back a Commons amendment tabled by backbench eurosceptics expressing "regret" that Mr Cameron failed to include a Bill enshrining the vote pledge in law in the Queen's Speech.
Downing Street has told ministers to abstain in the vote but is allowing other MPs, including parliamentary aides, a free vote, saying Mr Cameron was "relaxed" about them formally criticising his legislative package.
In his Daily Telegraph column Mr Johnson suggested legislation would mean "we will all have to focus not on the feud - so toxic, so delicious, so gloriously fratricidal - but on what is actually right for the country; on the nuts and bolts of
what we are trying to achieve".
"We are all going to have to wrap that cold towel round our heads and ask: do I want in or out? And why?" he said
Mr Johnson wrote that the EU was "no longer of key importance to the destiny of this country" as it focused increasingly on making the eurozone work, meaning it was right for Mr Cameron to seek a new deal.
But he added: "This renegotiation can only work if we understand clearly what we want to achieve: a pared-down relationship based on free trade and co-operation.
"And our partners will only take us seriously if they think we will invoke Article 50, and pull out, if we fail to get what we want. If we are going to have any chance of success in the negotiations, we need to show that the UK is willing to
The Article provides for a two-year negotiation on the terms of withdrawal, but allows a member state to pull out at the end of that period if no agreement has been reached.
Defence Secretary Philip Hammond earlier joined Education Secretary Michael Gove in saying he would back a British exit if there was an immediate referendum but both backed the Prime Minister's strategy.
Mr Gove said he was happy to contemplate cutting formal ties with the EU, suggesting he was in line with public opinion in feeling it would be "perfectly tolerable" and indeed bring some benefits.
Mr Hammond said: "I believe that we have to negotiate a better solution that works better for Britain if we are going to stay in."
Pressure for action from the Tory right has been fuelled by the growing electoral success and influence of the anti-EU UK Independence Party.and calls from several party grandees including ex-chancellor Lord Lawson for a UK exit.
Mr Hammond criticised their position as "defeatist" and said he believed Mr Cameron had a "reasonable chance" of securing sufficient reforms.
Mr Gove's parliamentary aide, Gavin Barwell, said he would be voting for the amendment in the Commons.
"I completely support the policy that was set out by the Prime Minister in January but what we need to do is to convince a sceptical electorate that we actually mean it," he told the BBC Radio 4 Today programme.
"The electorate at the moment doesn't have a great deal of trust in politicians in general and many people feel they have been promised referenda in the past and they haven't happened.
"So this isn't an issue about Conservative MPs trusting David Cameron. It's about using the legislative process to convince the electorate that the clear commitment he gave in his speech is going to happen."