The long and often erotic history of Jaguar luxury cars suffered a setback yesterday when the company's latest advertising gimmick was ruled "sexually suggestive" and a potential marriage-breaker.

Attempts to capitalise on Valentine's Day led to dozens of complaints about an unsolicited letter apparently from a would-be lover. Signed for men by an Elizabeth Jones and for women by an Ian Major, the letter speculated on such subjects as "what might drive you wild".

The effect of the campaign was alarming and stressful to many recipients who complained, according to the Advertising Standards Authority.

The ASA ruled that the advertising wheeze had not made it clear that the letter was a marketing ploy.

Jaguar apologised for causing offence and told the ASA it would not use the same approach again.