50/50 chance of quitting EU - Major
The UK is poised to leave the European Union unless there is genuine reform, former prime minister Sir John Major has warned.
In a frank assessment of the UK's relationship with Brussels, Sir John put the chance of a British exit from the European Union at "just under 50%" - but that probability would rise if David Cameron was unable to secure change before the referendum he has promised by the end of 2017 if he remains in Downing Street.
Sir John said frustration with the EU was no longer a "fringe opinion" in the UK and Brussels was often seen as showing a "lofty disdain" for British concerns.
But in a comment seemingly aimed at Mr Cameron over his tactics in Europe, Sir John said: "Wise negotiators will tone down the oratory and turn up the diplomacy."
In a speech in Berlin, the former prime minister, who faced bitter battles over Europe during his time in office, said he wanted to "sound the alarm" about the prospect of a British exit from the EU.
"What we must all realise is that a divorce may be final. Absolute. A reconciliation would be unlikely," he said.
Sir John pushed for a series of reforms and argued that freedom of movement - the measure which has allowed migrants from other EU countries to settle in the UK - had to be part of the negotiation.
He said absorbing the number of migrants currently projected to come to "our small island" is not "physically or politically possible without huge public disquiet".
He told members of German chancellor Angela Merkel's party that opposition to the EU in England had reached a "critical mass" and "for the first time there is a serious possibility that our electorate could vote to leave the EU".
"I put the chance of exit at just under 50%. But if the negotiations go badly, that percentage will rise. Conversely, with genuine reform, it will fall.
"I ask our European partners to realise we are close to a breach that is in no one's interest. Britain's frustration is no game.
"It is not a political ploy to gain advantages and concessions from our partners. There is a very real risk of separation that could damage the future of the United Kingdom - and Europe as a whole."
Sir John backed the Prime Minister's commitment to hold a referendum, saying it was time to settle the issue "once and for all".
A vote to remain in the EU would give the government "a fresh mandate to exercise our full influence in Europe".
But a decision to sever ties with Brussels would leave "no choice other than to obey our electors".
Reforms could benefit all 28 EU members, he said: "Of course there are unique British challenges at the moment, but the ideas of greater competitiveness, subsidiarity and democratic legitimacy work for everyone - and not just us."
Sir John stressed the UK would not accept "ever-closer" union and there needed to be protection for non-eurozone countries such as the UK.
But he said the controversial issue of freedom of movement also had to be addressed and claimed the UK's position had been "misunderstood".
The UK's population has grown by 7% in a decade and "matching migrants to the size of host countries, the UK has accepted one of - if not the - largest population movement in peacetime European history".
It is a "tribute" to the success of the UK that so many migrants want to come "but the sheer scale of the influx has put strains on our health, welfare, housing and education services that we struggle to meet - and has held down wages for many of the poorest members of our society".
Sir John added: "I do not wish to close our doors to strangers - especially strangers with skills from countries that are often allies. But I do recognise - reluctantly - that our small island simply cannot absorb the present and projected numbers at the current speed: it is not physically or politically possible without huge public disquiet."
He highlighted the UK's large net contribution to the EU's budget as a reason why the country's concerns should be "treated with consideration", warning "it can only inflame resentment if we are told our concerns are non-negotiatable and we must toe the line".
The UK does not want to end free movement, merely to qualify it, he said. "It is not too fanciful to say that our partners must weigh up a choice: help us on this issue or deny us - knowing that the latter course can only fuel the Eurosceptic argument."
Migration has also caused problems in other countries, fuelling the rise of single-issue parties across Europe. "Some are racist. Others are borderline racist. Some are merely bigots," he said.
Speaking at an event in central London, Labour leader Ed Miliband said: "I think John Major's speech is a pretty damning indictment of David Cameron because you've got John Major, who basically believes in Britain remaining in the European Union, saying - in not very coded terms - that the Prime Minister's strategy is burning alliances and burning bridges and not helping Britain in Europe. And that is completely right.
"We know what threatening exit did - you got a perfect test case around Jean-Claude Juncker where David Cameron lost by 26 votes to two.
"And why did he lose that vote in the way he did? Because anything associated with David Cameron in Europe is toxic.
"They basically think that if David Cameron is supporting it, it's because of the problems of the Conservative Party rather than the problems of Europe."