Latest poll shows 55% support for Britain remaining in EU

Support for remaining in the European Union stood at 55%, with 45% supporting a Brexit, according to an online Populus poll released on Twitter on Thursday while voting was under way in Britain's referendum.

Populus said the survey of 4,700 was carried out on Tuesday and up to midnight on Wednesday night.

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Investment bank JP Morgan said its analysis of recent opinion polls on Britain's European Union membership referendum showed the "In" camp was narrowly ahead on Wednesday, a day before Britons go to the polls.

On the basis of the data in hand, our clean-up process suggests a 2 percentage-point lead on average for 'Remain' in the polls published this week, with around 9 percent of the vote undecided," J.P. Morgan economist Malcolm Barr said in an email.

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"Our measure of the trend through the week-to-week noise now sits at a 0.6 percentage-point lead for 'Remain'." Barr added that "subjectively", he saw a roughly 45 percent chance Britain would leave the EU compared to the 25 percent chance priced into betting markets.

British PM David Cameron has repeatedly urged people to vote to remain in the EU.