LONDON -- With speculation growing about Britain's future in the European Union, Tony Blair, the former prime minister, warned Wednesday that the country faced a "real and present danger" if it edged toward leaving its regional alliance while power shifts to emerging economies.
Speaking in London, Mr. 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 so-called Euroskeptics in the ascendancy.
Addressing a business lobby group, Mr. Blair said Europe was an "absolutely essential part of our nation remaining a world power," and added that it would be a "monumental error of statesmanship to turn our back on it."
Critics questioned the impact of Mr. Blair's speech, suggesting his credibility at home had been damaged by his involvement in the invasion of Iraq, and because he was once an enthusiast for membership of the euro, which has suffered an acute debt crisis.
But the intervention of such a high-profile figure suggested that the pro-Europeans were worried enough about the tenor of the debate in Britain to launch a fight against the skeptics for fear of losing the argument by default.
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.
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.
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 EU and urged business executives who do favor staying in the bloc to speak out.
Mr. Blair contended that arguments to leave the bloc crossed a "chasm of error" and advocated 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," Mr. Blair said.
He added that given the global shift of power from West to East, Britain's influence could only be maximized through the collective heft of the union, with its combined population of around 500 million.
Changes in the global economy had 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, Mr. Blair said in his speech to Business for New Europe, an organization lobbying for continued British membership in the bloc. If it did quit, Mr. Blair suggested, Britain might spend the next 20 years trying to get back into the EU.
"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. Its population is three times that of the whole of the EU. India has over a billion people."
Nigel Farage, leader of the UK Independence Party, which wants Britain to quit the bloc, said it was "remarkable" to hear a man who "was responsible for an illegal war talk about statesmanship."
But membership in the European Union wasn't the only issue debated among the country's political classes. On the eve of a major report into Britain's phone-hacking scandal that editors and journalists fear could lead to statutory regulation of the press, a group of more than 80 British lawmakers on Wednesday launched a defense of press freedom which, they said, would be undermined by new laws enforcing controls on newspapers.
"As parliamentarians, we believe in free speech and are opposed to the imposition of any form of statutory control even if it is dressed up as underpinning," the group of 86 legislators, who were from the three main parties and both houses of Parliament, said in a letter published in The Guardian and The Daily Telegraph.
The letter appeared the same day a van pulled up at 10 Downing Street with Mr. Cameron's personal copy of the report, which has emerged from nine months of hearings conducted by Lord Justice Brian Leveson after the hacking scandal that focused primarily on Rupert Murdoch's British newspaper subsidiary.
The document, to be made public today, is likely to stoke a furious debate within the divided political elite about the future of press controls. These are currently based on a loose, voluntary system of self-regulation administered by the newspaper industry through a body known as the Press Complaints Commission, which many lawmakers and a cross section of newspaper editors believe has for years been woefully ineffective.