Britain will walk away from negotiations with European Union partners if its pleas for immigration reform are ignored, raising the real possibility of leaving the bloc altogether, Foreign Secretary Philip Hammond said Friday.

Hammond told the Daily Telegraph that the British public could vote to end the country’s membership unless there was “substantial, meaningful reform” from Brussels.

Prime Minister David Cameron has promised an in-out referendum for 2017 if his Conservative Party wins next year’s general election, but has failed to win support for border reforms from fellow European leaders.

German Chancellor Angela Merkel last week warned her British counterpart that he was approaching a “point of no return” with the EU over his immigration proposals, according to a German news report.

However, Hammond insisted that there would be no turning back, saying that Britain would be “prepared to stand up from the table and walk away” if its proposals were not considered.

“We have to be prepared to. In this case it isn’t even our decision because there’s going to be a referendum at the end of this process,” he said in comments published on the Telegraph’s website.

Eurosceptic Hammond promised to be “candid” with EU partners and to warn them that the British public were expecting results.

“I’d like to be telling my German counterpart honestly, if you draw the line there, I don’t think we’re going to get this past the British public in a referendum — but if you could move your line to there, I think we might.”

He ruled out talk of quotas on the amount of immigrants coming to Britain from the EU, but suggested he may raise the idea of “a mechanism that delivered the same kind of outcome”.

The Conservatives are struggling to open up a lead over the embattled Labour Party due to the loss of supporters and MPs to the anti-EU UK Independence Party, and Hammond’s appointment was widely seen as an attempt to woo back disgruntled voters.

But the party is expected to suffer defeat in Thursday’s by-election in Rochester, south England, triggered by the defection of Tory MP Mark Reckless to UKIP.