The pop superstar, Robbie Williams has been rebuffed by advertising watchdogs over his claims that Mars used his picture without permission in a campaign, endangering an endorsement deal he was negotiating.
But the singer succeeded in having the confectionery giant carpeted over misleading claims that it could provide VIP tickets to seem him in concert as competition prizes.
The row followed competition in the News of the World inviting readers to complete a sentence describing their dream start to the millennium. The ad featured a large photograph of Williams and the caption "See Robbie live".
Lawyers representing Williams complained to the Advertising Standards Authority that the picture was used without his authority and that the ad implied and he endorsed Mars products.
They also claimed that, at the time the ad appeared, Williams's 2000 concert schedule had not been arranged and there were no decisions about who would get VIP tickets.
Mars claimed the use of Williams photograph, whose copyright was owned by the News of the World, infringed no legal rights. It also insisted the ad had not implied the singer endorsed its products and was unlikely to affect his negotiation of genuine endorsements.
But the ASA ruled that Mars was guilty of exaggeration after it admitted that, although the closing date for competition entries had been 31 December 1999, it could not guarantee the availability of VIP concert tickets after 17 September.
Meanwhile, a dotcom sportswear company whose poster showed a runner vomiting into a rubbish bin has been cleared by the ASA of offensive advertising.
The ASA said the ad, produced by BMP DDB for boo.com, realistically showed the effect of strenuous exercise on people unused to physical activity.