LONDON (Reuters) - Citi researchers said on Wednesday they believed Britain would vote on Thursday by a close margin to remain in the European Union but that such a close vote could still undermine political stability in both the United Kingdom and the 28-member bloc.

"We see a 60 percent chance that the majority of British voters will choose 'Remain' in the 23 June EU referendum," Citi said in a research note to clients. "A 'Close Remain' (our base case) could still undermine UK/EU political stability."

"A vote to 'Leave' would have major repercussions in global financial markets, the economy and politics, triggering substantial downward revisions of UK and European growth forecasts," Citi said.

The implied probability of a vote to remain in the European Union was 75 percent, according to Betfair betting odds.

(Reporting by Guy Faulconbridge; editing by Michael Holden)