LONDON (AFP) - Voting has ended in Thursday's historic British referendum on EU membership, with the final opinion poll pointing to a slender victory for the "Remain" campaign.

A YouGov survey conducted on Thursday found 52 per cent were backing Britain's membership of the European Union, and 48 per cent wanted to leave.

"The results are close and it too early to call it definitively," said Joe Twyman, YouGov's head of political and social research.

"But these results, along with the recent trends and historical precedent, suggest a Remain victory is the more likely outcome."

YouGov spoke to 4,772 people it had surveyed on Wednesday to find out how they actually voted on the day.

"The survey found a small move to 'Remain' and based on these results we expect the United Kingdom to continue as a member of the European Union," Twyman said.

"Remain are on 52 per cent with Leave on 48 per cent."

The survey was released as polling stations closed at 2100 GMT.