[LONDON] The EU referendum is the biggest political event in British history, according to the bookmakers, who are putting their money on a vote for Britain to stay in on Thursday - contradicting opinion polls.
"I would be absolutely flabbergasted if the UK electorate vote to leave the EU," Barry Orr, a spokesman for online betting exchange Betfair, told AFP.
Betfair has matched bets worth nearly 60 million euros (S$91 million), surpassing the 40 million euros matched on the 2012 election of US President Barack Obama.
The company was offering odds, which include a profit and therefore cannot be compared directly to polls, with an implied probability of 74 per cent for "Remain" on Wednesday.
Bookmaker William Hill said it had taken bets worth £20 million (S$30.3 million), another record, and was offering a 76 per cent chance of "Remain" Wednesday.
"The EU referendum is set to overtake the Scottish referendum (in 2014) as the biggest political betting event of all," said spokesman Graham Sharpe.
However, he noted that the odds had lengthened during the day from an 81-per cent chance.
Wednesday saw the publication of two new opinion polls giving a slight lead to the campaign to leave the EU, leaving pollsters warning the vote was too close to call.
Who to believe? The bookmakers correctly called the defeat of the independence side in the 2014 Scottish vote, when some polls had put them ahead.
The bookies were far closer to the correct result in last year's general election, when Prime Minister David Cameron's Conservatives won a majority after weeks of opinion polls showing the election was too close to call.
"Before the eve of the Scottish referendum, the prices were very similar to what they are for the UK referendum: one to three, implying that 75 per cent chance of a victory," said Betfair's Orr.
"The market would suggest that 55 per cent of the UK electorate would vote to remain in the EU." Matthew Shaddick, head of political betting at Ladbrokes, sounded a note of caution, however.
"The truth is, we don't really have enough evidence to be sure how predictive political betting markets really are," he wrote in an online article for the Daily Telegraph.
"It's only in recent years that we've seen the sort of big, liquid, multi-million pound events that could produce anything worth studying." He added that if he were betting on Wednesday, he would back "Leave".
"I still think 'Remain' are the more likely winners, but there's enough uncertainty in this vote to make me think the outsiders have a better chance than the odds imply," he wrote.