Britain leader David Cameron vows to let voters decide on EU LONDON - Laying out a vision that could lead his country out of the European Union, Prime Minister David Cameron vowed Wednesday to negotiate a new relationship with the 27-nation trading bloc and put Britain's continued membership to a national vote. In possibly the most important speech of his premiership so far, Cameron said many of his compatriots were fed up with growing centralization of power in Brussels and that a new deal was necessary. He pledged to try to win concessions for Britain and then let voters pass judgment, by the end of 2017, in a referendum on whether they wanted to remain in the EU. A withdrawal could jeopardize Britain's access to European markets and diminish its influence on the world stage, particularly its role as a bridge to Europe for the United States. But Cameron called the status quo unacceptable to too many Britons and said a fresh mandate from voters to stay in the EU was imperative. It is time for the British people to have their say. It is time for us to settle this question about Britain and Europe," Cameron said. Democratic consent for the EU in Britain is now wafer-thin.... That is why I am in favor of having a referendum. He has to win another term as prime minister first, in an election due in 2015. His Conservative Party will run on a platform making a plebiscite an immediate priority upon a return to power, Cameron said. Such a referendum would be the first time in about 40 years that Britons had a direct say on their status within Europe, a topic that has inspired deep ambivalence in this island nation for decades. Winston Churchill used to say about Europe that Britain was "in it" but not "of it"; the country's EU entrance in 1973 was a hand-wringing affair from the start. Cameron emphasized his own support for Britain's continued membership - albeit on more favorable terms - in the EU, which offers free movement of goods and people across the world's biggest trading bloc, comprising 500 million people. "I am not a British isolationist, but I do want a better deal for Britain," he said. I want the European Union to be a success, and I want a relationship between Britain and the European Union that keeps us in it. But he sidestepped the question of whether he would advocate withdrawal instead if he failed to extract concessions for Britain from other EU nations. He also failed to specify which powers he wants to reclaim from Brussels, though many Conservative lawmakers have been exasperated by European directives in areas such as social and employment policy. A few recent polls here have shown more Britons in favor of exiting the EU than staying put. But the gap has narrowed in the last week or two as the issue began to dominate headlines in advance of Cameron's speech and as high-profile business leaders and politicians stepped up warnings of adverse consequences of a pullout. Together, EU nations form Britain's biggest trading partner. Tens of thousands of Britons live and work in other European countries without need of a visa; conversely, Britain-based firms have enjoyed access to cheaper labor because of the inflow of migrants from across the English Channel, especially from Eastern Europe. "He is going to put Britain through years of uncertainty and take a huge gamble with our economy," Ed Miliband, the leader of the opposition Labor Party, said Wednesday during a raucous session of Parliament. Miliband accused the prime minister of "running scared" of the UK Independence Party, or UKIP, an explicitly anti-EU grouping whose brisk rise in the polls in recent months threatens to siphon votes from the Conservatives. Miliband also knows that the issue of Europe poses a risk for his own party, which could find itself forced by popular demand to accede to a referendum if it wins the next election, then paying the price for a detrimental outcome. So far, Labor has been cagey about whether it would put EU membership to a national vote. Besides UKIP, Cameron is under acute pressure from within Conservative Party ranks, which are now populated by "Euroskeptics" demanding a looser relationship with the EU or outright withdrawal. His speech Wednesday had been anticipated for months but was repeatedly delayed as he tried to figure out just what to say on an issue that has vexed British leaders for decades, particularly Tory ones. Cameron himself jokingly described the long wait as "tantric." In an unusual move, the U.S. publicly declared before the speech that Britain would be a less valuable partner out of the European Union, and leading officials across the Continent pointedly warned London not to expect to dictate terms to the rest of the EU. Some have also expressed open resentment of perceived British obstructionism as they fight the grave threat posed by the euro debt crisis. Cameron acknowledged that Britain's hesitancy and hostility toward the EU has frustrated other member states, but he said the bloc ought to be flexible enough to accommodate countries seeking deeper integration, such as the 17 nations that share the euro currency, and those in favor of a more detached relationship. He said Britain's focus would remain on strengthening the EU's original identity as an economic grouping marked by the free trade of goods and services. The moves toward greater political harmonization, with increasing powers for Brussels in areas such as public debt and spending, are what many Britons object to, seeing them as encroachment on national sovereignty. Likewise, Britain has clung tenaciously to the pound as its currency, as a symbol of independence. European officials say that they value Britain's strong voice on economic liberalization and that the loss of one of the EU's largest economies from the club would be a blow. But efforts by Britain to adopt only those elements of cooperation that suit it will run into resistance from other EU capitals, which say that "Europe a la carte" is not on the menu. "Not all and everything must be decided in Brussels and by Brussels," said Guido Westerwelle, the German foreign minister. But cherry-picking is not an option. Cameron tried to soothe ruffled continental feathers by drawing attention to shared experiences, including the Napoleonic Wars, the Industrial Revolution and the battle against Nazism. "We have helped to write European history, and Europe has helped to write ours," he said. At the same time, "our geography has shaped our psychology" as an island nation, Cameron added. We can no more change this British sensibility than we can drain the English Channel. He insisted that it was right to seek a renegotiated relationship with Europe and a new framework for the EU, even though some might regard that as political "heresy." "In its long history, Europe has experience of heretics who turned out to have a point," Cameron said.