The mounting scandal over racist and sexist comments by radio personality Don Imus offers another reminder of the unpredictability that advertisers face when they support controversial programmes on radio and television.

Three advertisers, Procter & Gamble, Staples and Bigelow Tea, announced this week that they would withdraw support from Mr Imus's programme after he referred last week to the members of the Rutgers University women's basketball team as "nappy-headed hos", a derogatory phrase referring to African-American women.