Of the UK's £8.7bn adspend, £1.1bn is accounted for by WPP subsidiaries.
WPP's power is bound to draw comparisons with Tesco, whose stores get £1 of every £8 spent in UK shops.
The figures from Nielsen Media Research show how WPP in particular and the big four holding companies in general now control a massive slice of total billings.
WPP's share accounts for 12.7% of total billings. Its biggest rivals, Omnicom, Publicis Groupe and Interpublic, control just over 27% between them.
Last week, WPP announced a 15% leap in 2004 profits to £546m and a 5% increase in billings to £19.6bn.
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