The survey by polling firm YouGov showed that if a referendum were held immediately, 46 percent would vote to remain, 39 percent would vote to leave, and the rest either did not know, would not vote, or refused to answer the question.

When the undecided and those who refused to answer were removed from the sample, the split was 54-46 in favor of remaining.

That is broadly in line with other polls in recent months which show a deeply divided electorate, in which opinion has swung slightly towards remaining in the EU. The 2016 referendum voted 52 to 48 percent in favor of leaving.