LONDON (BLOOMBERG, AFP) - The pound has dropped the most since 2009, as early results in Britain's European Union referendum punctured confidence the "Remain" campaign was heading for victory.

Britain's currency tumbled against all of its major counterparts, and FTSE 100 Index futures contracts slid after results from two industrial cities in northeast England showed greater support for leaving the bloc than academics had forecast.

While opinion polls have said the race is neck and neck, markets worldwide have rallied in the past week as a general consensus emerged that the country would vote to remain.

However, sterling, which had touched a 2016 high of US$1.50 barely two hours earlier, slumped to just below US$1.43 after returners announced the northern town of Sunderland had seen a stronger performance than expected for the pro-exit camp.

That came after news that nearby Newcastle had seen a smaller-than-forecast win for "Remain". Investors took fright at the initial results, sending them rushing for lower-risk investments, with the dollar tumbling to just above 103 Japanese yen from around 106.80 yen.

The pound has depreciated 4 per cent against the Singapore dollar and 6.5 per cent against the yen.

Price swings in the British currency accelerated as the first results from the referendum filtered through, with sterling trading in a range of more than 4 per cent.

It earlier climbed above US$1.50 for the first time since December after a nationwide YouGov survey conducted on the day of the vote showed a 52 per cent share for the status quo, and also sank as much as 3.9 per cent.