Danny Alexander, George Osborne's Liberal Democrat deputy, is risking a new coalition rift by using official Treasury analysis to more than three million British jobs would be at risk if Britain left the European Union.
Alexander, the chief secretary to the Treasury, is reported to have faced pressure from Osborne's aides to not make the official analysis public that suggested that 3.3 million jobs were connected to Britain's membership of the political bloc.
This comes as David Cameron fights a desperate battle to stop former Luxembourg premier Jean-Claude Juncker becoming president of the European Commission, even raising the prospect that Britain could be forced to leave the EU over the issue.
Juncker mocked the Prime Minister for his lack of "common sense" and said he expected to be anointed president this week. Meanwhile, Lib Dem business secretary Vince Cable rounded on Cameron for weakening Britain's "punch" in Europe by stoking a row over Juncker's appointment.
“The way it’s been done, unfortunately, has not helped Britain punch its weight in Europe,” he said.
Speaking in Washington today, Alexander will use Treasury analysis to warn about how many jobs are at stake if Britain leaves the European Union.
“When the focus is on jobs, and growth, and wider risks we take with our prosperity through isolation then the argument can and will be won," he is set to say.
“Indeed, the latest Treasury analysis shows that 3.3 million British jobs are connected to Britain’s place in Europe. That is the measure of the risk that isolationists would have us take.”
“So pro-Europeans should be confident that the British public will not vote to leave the EU in the event that a referendum on our membership is called. British people want the jobs and opportunities that come with staying in the EU.
“They want Britain to continue leading in Europe and they want Britain to remain a leading voice on the world stage.”
Mr Alexander will say that it would be “foolish to turn our backs” on the EU.
“This isn’t some starry-eyed, unconditional affinity for the EU. The EU has flaws and it must reform… But Britain can only reform it by taking our place at the table, rolling up our sleeves and getting to work. By leading in Europe, not threatening to leave it.”
Others poured scorn on the Treasury analysis, like Ryan Bourne, head of public policy at the Institute for Economic Affairs, who branded it "deliberately disingenuous".
.@PhillipSouta deliberately disingenuous. Jobs linked to free decisions of individuals and businesses, not membership of political union.
— Ryan Bourne (@MrRBourne) June 25, 2014
Labour's shadow Treasury minister Cathy Jamieson welcomed the Treasury analysis, concluding that "leaving the EU would be a disaster for jobs and businesses in Britain.
"It’s no wonder George Osborne tried to stop it being published when he and David Cameron are putting their own party’s interest before the national interest when it comes to Europe.
"Labour wants reform in Europe to make Europe work better for Britain, but walking away from our main trading partner would put millions of jobs at risk."
The Ukip leader and MEP is the most famous 'outer'. After his party took over a 100 council seats in May's local election's Nigel Farage is hoping to win the 2014 European elections and then gain MPs in Westminster in 2015. He has confirmed he will seek a parliamentary seat himself.
Margaret Thatcher's former chancellor and a true 'Tory grandee' revealed in The Times that if and when there is a referendum "I shall be voting out". He also stuck the boot into the David Cameron by saying the prime minister's attempts to renegotiate the terms of the UK's relationship with the EU would be "inconsequential".
There are quite a few Conservative MPs who would like to wave goodbye to Brussels. Ken Clarke has said the figure is as low as 30 despite the strong eurosceptic feeling on the backbenches. However the exact number is not clear. Mid-Bedforshire MP Nadine Dorries, who remains suspended from the Conservative Party, is currently talk tof the eurosceptic town amid rumours she may defect to Ukip. Other backbench Brexiters include Bill Cash, Douglas Carswell, Peter Bone and Philip Davies and former defence minister Sir Gerald Howarth.
Most of the anti-EU focus is on the Tory benches. But there are more than a handful of Labour MPs would would like to quit Brussels as well. Eurosceptics include Frank Field, Kate Hoey, Austin Mitchell, and Gisela Stuart. Stuart has argued the status quo is "not sustainable" and Britain should leave.
Rupert Murdoch has warned that the EU will "sink" the UK. The News International and boss caused a stir when he met Nigel Farage for dinner in London recently and said the Ukip leader was "reflecting opinion" with his anti-EU views. In November 2010 Richard Desmond’s Daily Express became the first UK newspaper actively to call for Britain to leave the EU, launching a ‘Get Britain Out’ campaign
Of course no campaign is complete without a bit of star power. The pro-EU camp have Eddie Izzard, who do the Brexiters have? Joan Collins, a 'patron' of Ukip, wants the UK to leave. "The EU, controlled from Brussels, cares only about itself," she said in March.
Most business leaders do indeed seem content with what Lawson called the "warm embrace of the European single market", but there are a few dissenters. Private equity guys Jon Moulton and Edmund Truell are two and Next boss and Tory peer Simon Wolfson has said: "Britain should stay in Europe, but only on the right terms".
There are a number of loud voices whinnying on the sidelines to say "neigh" to the EU notably Melanie Phillips, Richard Littlejohn, Tom Utley, Simon Heffer. Basically the Daily Mail stable.
Several high-profile politicians appear to be on the verge of calling for the UK to exit the EU - but just are not there yet. Former defence secretary Liam Fox - pictured here with a big gun - has said "life outside the EU holds no terror" should David Cameron's hopes of negotiating a new treaty fail. Education secretary Michael Gove is said to have told friends the UK has "nothing to be scared of" by leaving Europe. And many other eurosceptic cabinet ministers, including Iain Duncan Smith and Owen Paterson are likely to share that view.