LONDON — With power shifting toward the world’s emerging economies, Britain faces a real and present danger if it edges toward the exit of the European Union, its regional alliance of 27 nations, Tony Blair, the former British prime minister, warned Wednesday.
Speaking to a business lobby group in London, Blair entered the fraught debate about his country’s place in the union with a speech arguing that the bloc was more important now than ever because it helped Britain leverage its influence within a changed geopolitical landscape.
Britons have rarely shown much enthusiasm for the idea of European integration, but in recent months discussion over Britain’s relationship with — or even membership in — the 27-nation European Union has intensified, with euroskeptics in the ascendancy.
Prime Minister David Cameron has said he wants to redefine ties with the European Union to create a looser bond based more clearly on its single economic market, and to put the outcome of that negotiation to the voters, possibly in a referendum.
And after almost three years of crisis for the euro, used by 17 of the bloc’s 27 members but spurned by Britain, there is more talk than ever before of a possible British exit from the union.
But Blair argued in his speech that the logic of suggesting that the right response to the euro crisis was to leave the bloc was to cross a ‘‘chasm of error’’ and to advocate a policy that was ‘‘politically debilitating, economically damaging, and hugely destructive of Britain’s long-term interests.’’
“Our country faces a real and present danger by edging towards the exit,’’ Blair said.
Europe was an ‘‘absolutely essential part of our nation remaining a world power,’’ and it would be a ‘‘monumental error of statesmanship to turn our back on it,’’ he said.
Last week, Roger Carr, the president of the Confederation of British Industry, Britain’s biggest business lobby, warned of the growing risk that the country would leave the union and urged business executives who favor staying in the bloc to speak out.
Against that backdrop, the intervention of Blair, who is a supporter of close ties between Britain and the European Union, is a sign of the concern among Britain’s pro-Europeans that they may be losing the argument for membership by default.
In his speech Blair argued that, given the global shift of power from west to east, Britain’s influence could be maximized only through the collective heft of the European Union, with its combined population of around 500 million.
Changes in the global economy have made the bloc more relevant than it was when Europe’s integration began 60 years ago as a project to reconcile a war-torn continent, Blair said in his speech to Business for New Europe, an organization lobbying for continued British membership of the bloc.
If it did quit, Blair said, Britain might spend the next 20 years trying to get back in.
‘‘Power is shifting west to east,’’ he said. ‘‘China has emerged finally, with its economy opening up, which will grow eventually to be the world’s largest.”