Sunday Surgery is presented by Letitia and Dr Mark Hamilton

The adverts, played at 4.20pm, included "sounds of graphic sexual moans and groans", were trailers for advice show Sunday Surgery.

The BBC said the ads formed part of a safe sex campaign on the show.

But Ofcom said the trailers, which attracted 14 complaints, were "totally inappropriate" and found the BBC in breach of its guidelines.

Our concerns were with the style and sexual explicitness of the promotions Ofcom

The trailers, which were broadcast in September, were aimed at 16 to 24-year-olds.

They broke into normal music programming and were designed to sound like radio interference from another station.

Many of the complainants believed they had heard an illegal broadcaster interrupting Radio 1 transmission.

One trailer said: "Dirty hot babes all over the UK looking for you to make their body rock", while another said: "Call me now - I've got lips to leave you breathless and a body to make you moan".

The BBC said the adverts were scheduled to avoid times when the youngest children would be listening, adding that the subject matter would have "passed over the heads" of young children.

The BBC added: "The campaign was felt to have a clear and serious educational purpose.

"Given the statistics for teenage pregnancy and sexually transmitted diseases, the BBC believed that some explicitness was justified as a way of attracting the attention of those most at risk."

'Misjudgement'

But Ofcom ruled: "We have no issue with the points that the BBC make about the merits of a campaign that seeks to address the important subject of sexual health among young people.

"Our concerns were with the style and sexual explicitness of the promotions. The material 'came from nowhere' and appeared to be genuine interference.

"In Ofcom's view it was totally inappropriate given the content and tone of the promotion for transmission at that time of day, when younger listeners would have been in the audience," the watchdog concluded.

"Overall, despite the BBC's best intentions, we consider that the scheduling of such a promotion when younger children would have been in the audience was an editorial and compliance misjudgement."