British Prime Minister David Cameron Resigns

Britain has voted to leave the European Union, forcing the resignation of Prime Minister David Cameron and dealing the biggest blow to the European project of greater unity since World War Two.

Global financial markets plunged as results from Thursday's referendum showed a near 52-48 percent split for leaving.

The pound fell more than 10 percent against the dollar to levels last seen in 1985, its biggest one-day fall in history, on fears the decision could hit investment in the world's fifth-largest economy, threaten London's role as a global financial capital and usher in months of political uncertainty.

European shares plummeted more than 8 percent, headed for their biggest ever one-day fall. Billions of dollars were wiped off European banks' market value, with Britain's Royal Bank of Scotland, Barclays and Lloyds Banking Group among the biggest fallers.

An emotional Cameron, who led the "Remain" campaign but lost the gamble he took when he called the referendum three years ago, said he would resign as prime minister by October.

"The British people have made the very clear decision to take a different path and as such I think the country requires fresh leadership to take it in this direction," he said in a televised address outside his Downing Street office.

"I do not think it would be right for me to be the captain that steers our country to its next destination."

Quitting the EU could cost Britain access to the EU's trade barrier-free single market and mean it must seek new trade accords with countries around the world. The United Kingdom itself could break apart, with leaders in Scotland -- where nearly two-thirds of voters wanted to stay in the EU -- calling for a new vote on independence.

The EU for its part will be economically and politically damaged, facing the departure not only of its most free-market proponent but also a member with a U.N. Security Council veto and powerful army. In one go, the bloc will lose around a sixth of its economic output. Populist leaders in France and the Netherlands demanded their own referendums to leave.

The vote will initiate at least two years of divorce proceedings with the EU, the first exit by any member state. Cameron, who has been premier for six years, said it would be up to his successor to formally start the exit process.

His Conservative Party rival Boris Johnson, the former London mayor who became the most recognizable face of the "leave" camp, is now widely tipped to seek his job.

Cameron, 49, Britain's prime minister for six years, gave no detailed timetable for his departure but said there should be a new leader by the time his Conservative Party holds its annual conference in October.

"This is not a decision I've taken lightly but I do believe it is in the national interest to have a period of stability and then the new leadership required," he said.

"I think it's right that this new prime minister takes the decision about when to trigger article 50 and start the formal and legal process of leaving the EU," he said. Article 50 of the EU's Lisbon Treaty deals with the mechanism for departure.

As he spoke under the gaze of cameras crammed into the narrow London street, celebratory horns sounded from cars passing nearby and "Leave" supporters marked their victory by waving Union Jack flags.

Cameron took office in 2010 as leader of a coalition government and in May last year won a second term with a surprise outright majority at a national election. He had been due to serve as prime minister until 2020.

He said he believed he had made "great steps" during his time in office, citing, among other things, his landmark move to legalise gay marriage in Britain.

"I love this country - and I feel honoured to have served it ... I will do everything I can in future to help this great country succeed," he said before taking his wife's hand, turning away and walking back into Number 10 Downing Street.