It found that Cancer Research UK had increased its brand value to £202m from £182.5m last year.
Cancer Research UK executive director of policy and comms Maxine Taylor said the brand value figure was close to the amount spent by the charity on research in 2005.
Last year's winner, The National Trust, slipped to second place in the 2005 rankings with £196m. Its winning value in 2004 was £203m.
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