DAVID Cameron has promised real change on Europe and a real choice in effecting that change.
However, he left Tory Eurosceptic MPs guessing what the details of his proposal will be when he makes an eagerly-awaited keynote speech later this month on Britain's membership of the European Union.
The Prime Minister, who has repeatedly said he wants the UK to remain a member of the EU and is against a straight in-out referendum, appears to be edging towards promising a poll in the Conservatives' next General Election manifesto but on keeping Britain in Europe on new terms.
Last month, The Herald reported how senior party figures warned that unless Mr Cameron promised an in-out referendum, his leadership would be challenged before the next election.
One senior source close to the PM said: "Most Conservative MPs and, indeed, most of the country now believe we need an in-out referendum and that if our membership is to survive it has to be on new terms.
"We have to get back to something like the Common Market; the status quo is not an option. The Prime Minister will have to accede to our demands."
Asked if Mr Cameron's leadership would be under serious threat without such a pledge, the insider replied: "Yes. We realise we can't do anything on staging a referendum this side of the General Election [because of the LibDems] but there should be a clear commitment in our manifesto.
"If Britain doesn't get what it wants, then we'll leave.
"It's now 50/50 as to whether the country will be in the EU in 10 years' time.
Tory backbencher Philip Davies insisted an in-out referendum on membership was now inevitable and argued an in-in poll, offering the status quo, would be a joke.
His colleague Stewart Jackson also demanded an in-out referendum, adding: "People's patience has run out. If he can't deliver on Europe, people will judge him quite harshly and he should be wary of putting himself in that position."
Asked by the BBC if a public vote could involve the option of withdrawal, the Prime Minister replied: "You will have to wait for the speech but it will demonstrate very clearly that it is the Conservative Party at the next election that will be offering people a real change in terms of Europe and a real choice about that change."
He conceded any renegotiation would be "tough" but said it was neither in Britain's national interest to withdraw nor adopt a so-called associate status where it would no longer be "round the table writing the rules".
Mr Cameron said: "I don't think it's right to aim for a status like Norway or Switzerland, where basically you have to obey all the rules of the single market but you don't have a say over what they are."
Herman Van Rompuy, President of the European Council, has warned British attempts to claw back powers from Brussels would put the future of the single market at risk.
Cherry-picking policies, he said, would see the EU "unravel". The PM said it was perfectly legitimate to seek to use the EU's need to reform and shore up the euro to reshape Britain's membership.
In response, Nigel Farage, leader of UKIP, the anti-EU party, claimed Mr Cameron was begging at the top table in Brussels for small changes. He said: "We are talking about a matter of trust.
"He sits there and thinks his great extended tease about this forthcoming Europe speech is entertaining – it is not."
"No matter what he says now, after so many broken promises, so many 'cast-iron guarantees', can anybody honestly believe that he will be telling the truth this time?
"The simple fact is that he wants us to stay in the EU no matter how it is configured.
"Of course we must talk to our European friends, of course we must do business with them, but we must do so from a position of strength, rather than weakness. That strength will be provided by being independent and masters of our own destiny rather than begging at the top table for a little bit of renegotiation here and a little bit of repatriation there."