** Shares of British property portal Rightmove Plc RMV.L
fall as much as 14.2% to 493.8p, their lowest since June 23
** Stock among top pct losers on FTSE 100 .FTSE index
** Shares fall on concerns over stronger competition after
U.S. real estate firm CoStar CSGP.O agreed to buy Rightmove's
smaller domestic rival OnTheMarket OTMPO.L
** Russ Mould of AJ Bell says CoStar was likely to use
OnTheMarket as a launchpad for a move into the UK market,
potentially leave Rightmove facing a new, more formidable
competitor
** Citi analysts say deal also makes unlikely that CoStar
could now consider buying Rightmove
** OnTheMarket surges more than 52% to 107.5p
(Reporting by Aby Jose Koilparambil and Prerna Bedi in
Bengaluru)
((abyjose.koilparambil@thomsonreuters.com))