The watchdog said the posters, for Liverpool's Lambrini perry, were likely to cause serious or widespread offence.

The ASA had 12 complaints about posters in the city's railway stations.

But the advertiser, Halewood International, said the sexual innuendo was "fun and harmless" and the campaign light-hearted and realistic.

Timed to coincide with Liverpool horse race the Grand National, it showed three women laughing, one with a glass in her hand.

Each poster featured one of four captions: "I love a man with a powerful beast between his legs", "Better to be on the jockey who comes last", "Leather boots and whips. Don't you just love a day at the races?", and "What I'd give for a well-trained stallion".

Halewood International said the wording was "suggesting the kind of banter" young women might have over a drink.

But the ASA ruled it must have future posters approved in advance for the next two years.