By Costas Pitas and James Davey
LONDON (Reuters) - Two polls on Saturday showed voters were still closely divided over whether to end Britain's European Union membership, a day after another survey put the 'Leave' campaign 10 points ahead, underlining the contradictory polling less than two weeks before the referendum.
The pound weakened by as much as 1.2 percent against the U.S. dollar immediately after an ORB poll for the Independent newspaper, showing a sharp swing toward a vote for Britain to exit the EU, was published on Friday evening.
Betting odds on Brexit also shortened after the survey, conducted on June 8 and 9, putting the 'Leave' camp 10 points ahead of 'Remain,' the latest in a run of polls to show rising support for a British exit from the EU.
But two surveys published on Saturday showed divergent results with one giving a two-point lead to supporters of Britain's EU membership and a second poll showing those in favor of Brexit were one point ahead.
Britons will vote in a June 23 referendum on whether to leave the world's largest free trade area, a decision with far-reaching implications for politics, the economy and trade but contrasting polls have made it difficult to predict the outcome.
An Opinium poll for the Observer newspaper, conducted between June 7 and 10, suggested 44 percent of Britons back continued membership of the bloc with 42 percent against and 13 percent undecided.
But a YouGov poll for The Sunday Times showed support for Brexit on 43 percent with those who wish to remain part of the 28-member trading bloc on 42 percent, a reversal on the previous survey released on Monday.
Contradictory opinion polls and a failure to predict last year's outright election victory for Prime Minister David Cameron's Conservatives have led financial markets to pay close attention to bookmakers' odds.
On Saturday, bookmaker Betfair cut the odds of a vote to stay, after the ORB poll, giving a probability of 70 percent, down from 78 percent earlier this week.
Bookmaker Ladbrokes said the ORB poll had caused it to shorten its odds on Brexit to 9/4 from 11/4 previously, implying a rise in the likelihood of a 'Leave' vote to 30 percent from 27 percent.
"We thought the Brexit rally was finished, but the 'Leave' odds have tumbled again on the back of the eye-catching 10-point poll," said a Ladbrokes spokesman.
However, Peter Kellner, the former president of polling company YouGov, suggested the ORB poll may not be the best indicator of public opinion.
"Tonight's YouGov and Opinium Research polls show little movement. Last night's ORB lurch to 10 percent Brexit lead looks like an outlier," he wrote on Twitter.
Friday's survey gave the Brexit camp its biggest lead since the poll series started a year ago, the Independent said. But the official Vote Leave campaign reacted cautiously, tweeting: "We don't believe the ORB online poll, our data suggests it's closer to 50-50."
The mixed picture has heightened market jitters about the outcome, with sterling repeatedly reacting to poll results.
Separately on Saturday, Britain's interior and foreign ministers responded to a media report suggesting visa rules for Turkish citizens could be eased by saying there were no plans to change the requirements.
Immigration has been a key driver of support for the 'Leave' campaign and ministers Theresa May and Philip Hammond said in an emailed statement it was "completely untrue" that "the UK is considering granting visa liberalization to some Turkish citizens."
(Additional reporting by Guy Faulconbridge and Bill Schomberg; Editing by Kevin Liffey and Bill Rigby)