UBS Warburg made the change over concerns on the impact of the downturn in advertising revenues on ad agencies.
The shares had a price of 165.5p when the market opened this morning, but dropped nearly 10p in morning trading to 156p.
Other media shares were also falling this morning, with WPP dropping from 668p to a low of 636p, before climbing slightly. Chime Communications, owner of HHCL and Bell Pottinger Communications, also dropped slightly, from 139.5p to 137.5p.
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