LONDON, May 31 (Reuters) - Option market bets on weakness in Britain's pound reached their highest in more than two months on Wednesday after an overnight shock to the exchange rate from a poll showing the ruling Conservatives falling short of a majority in next week's election.
The 1-month sterling-dollar risk reversal - a measure of the balance of bets for more weakness of the currency in the next month over those for more gains - was quoted at around -0.8, its most negative since March 15 .
Offered rates for the contract were as low as -1.013, the lowest since Feb. 10. (Writing by Patrick Graham, editing by Nigel Stephenson)