Prime Minister David Cameron is expected to offer British citizens a vote on leaving the European Union if his party wins the next election, a move sure to trigger alarm among fellow member states.

Cameron will be making his long-awaited speech on the United Kingdom's future relationship with Europe on Wednesday. It was postponed last week due to the hostage crisis in Algeria.

He will acknowledge that public disillusionment with the EU is “at an all-time high,” saying that the terms of Britain's membership in the bloc should be revised and the country's citizens should have a say.

Cameron will propose that the Conservative Party will renegotiate the U.K.'s relationship with the European Union if it wins the next general election, expected in 2015.

“Once that new settlement has been negotiated, we will give the British people a referendum with a very simple in or out choice to stay in the EU on these new terms. Or come out altogether,” Cameron will say, according to excerpts of his speech released in advance. “It will be an in-out referendum.”

The prospect of an “in” or “out” referendum _ and a possible U.K. exit from the EU _ will surely appease critics in Cameron's own party, which has seen deep divisions over Britain's relationship with Europe.

But it will undoubtedly trigger further alarm among business leaders and other EU member states and could leave Britain increasingly isolated in Europe.

Already, speculation over a possible referendum has prompted a chorus of concern from around the world, stressing the importance of Britain's presence in the bloc and warning about the economic consequences of a British exit from the bloc.

Even the U.S., which normally stays out of disputes among EU states, waded into the debate.

The White House said last week that in a phone call, President Barack Obama told Cameron that “the United States values a strong U.K. in a strong European Union.”

While Cameron will reiterate his view that Britain should stay in the EU, he will say that “democratic consent for the EU in Britain is now wafer thin.”

But he will caution against those seeking to hold a vote immediately, saying it would be wrong to hold a referendum immediately “before we have had a chance to put the relationship right.”

The timeline he will lay out mostly hinges on a Conservative Party victory in the next general election. Still, legislation will be drafted before 2015 so that if his party wins, legislation will be introduced and passed quickly enough to ensure a referendum could be held “in the first half” of the next Parliament, Cameron is due to say.

Cameron's Conservatives formed a coalition government with the Liberal Democrats after an inconclusive 2010 election. Pegging the possibility of a vote to an electoral win could be a gamble to appease increasingly vocal euroskeptics in the Conservative Party and stem the stream of voters who have jumped ship to the fringe UK Independence Party, which advocates EU withdrawal.

Ahead of the speech, opposition leader Ed Miliband had already fired a salvo. He said the speech would define Cameron as a “weak prime minister, being driven by his party.” (AP)