BUZZ-Cairn Energy: worst day post-GFC as tax dispute hits shares
** Cairn Energy (LSE: CNE.L - news) falls 16.6 pct, its worst day since Oct 2008, after Indian unit gets served a $1.6 bln tax claim
** Stock is worst performing UK mid-cap
** Company to appeal the decision
** Cut to "hold" from "buy" at Jefferies - says increased risk Cairn India stock will be lost to Indian govt - target price downgrades at least five brokers
** Second most traded on Stoxx 600 by average volume
(RM (LSE: RM.L - news) : alasdair.pal.thomsonreuters.com@reuters.net)