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By Jemima Kelly and Guy Faulconbridge
LONDON, May 19 (Reuters) - Betting odds on Thursday indicated the highest chance to date of Britain voting to stay in the European Union, with the implied probability of a vote for membership rising to as high as 83 percent.
William Hill (Other OTC: WIMHF - news) cut its odds an "In" vote to 1/5, the lowest level to date and indicating an implied probability of 83 percent, a spokesman said. Betfair odds indicated a 77.5 percent chance of an "In" vote, up from 70 percent last week.
As polls have given sharply different pictures of public opinion, many investors are watching betting odds closely. Odds have consistently indicated a high probability of an "In" vote in the referendum.
"Political punters suddenly seem to have made their minds up that, contrary to the opinion polls, 'Remain' is a rock solid bet," Graham Sharpe, a spokesman for William Hill said.
"William Hill have slashed their odds for a 'Remain' vote in the EU Referendum to their shortest level," Sharpe said.
An Ipsos MORI poll published on Wednesday found 55 percent of those surveyed supported staying in the EU while 37 percent wanted to leave and 8 percent were undecided, though other polls have shown the Out campaign in the lead. (Editing by Michael Holden)