LONDON Prime Minister David Cameron's promise of a vote on Britain's EU membership is a gamble he must take to end the bitter arguments that have poisoned British politics for decades, a predecessor who was seriously undermined by those rows said on Thursday.
John Major, a Conservative prime minister whose seven years in office were dogged by party infighting over Europe, said the referendum could "heal old sores".
Cameron, who lags in the polls, delighted his ruling Conservative Party's rebellious anti-EU wing last month when he said he would campaign for the 2015 parliamentary election on a pledge to renegotiate the terms of Britain's EU membership.
He said an "in our out" referendum on the country's membership of the bloc would then be held by the end of 2017 - provided he won a second term.
However, the plans upset some EU countries which are fed up with what they see as London's semi-detached stance. Even the United States, a close British ally, is opposed to a British withdrawal. British business leaders also said they were worried the uncertainty could weaken the economy.
"It is a gamble for the country and for the Conservative Party," Major said in a speech at the Chatham House thinktank.
"The relationship with Europe has poisoned British politics for too long, distracted parliament from other issues and come close to destroying the Conservative Party. It is time to resolve the matter."
The issue of Europe brought down Major's predecessor Margaret Thatcher in 1990 and divided the Conservatives throughout Major's time in office from 1990 to 1997, during which he faced repeated rebellions by eurosceptic party members.
Then, as now, eurosceptics wanted the British leader to take a stand against what they saw as an undemocratic, costly and meddling European superstate eroding British sovereignty.
Cameron will never sway those fervently opposed to Brussels, Major said, but he can persuade most voters that leaving the bloc would undermine trade and Britain's global influence.
The harder task will be to convince EU countries to hand back powers to London in areas like employment law, Major said.
"It is difficult and ambitious, but I do think the prime minister has some significant negotiating cards to play and I think it is possible to negotiate some of those changes," Major said. EU leaders do not want to lose one of the world's biggest economies and an important link to the United States, he said.
(Editing by Pravin Char)