Radio 1's Scott Mills show has been rapped by the broadcasting watchdog for broadcasting what appeared to be a swear word when children were listening.
Badly Bleeped TV, in which TV and radio clips are played with words bleeped out, has been a regular feature on the BBC station.
The sounds of the beginning and end of the words remain audible, giving the impression that the bleep is masking an offensive word.
But it is later revealed that the words, such as fated and fantastic, are not offensive.
The BBC said that the feature belonged to "the saucy seaside postcard tradition of comedy" and not to "anything more offensive".
But Ofcom found that Radio 1 had broadcast the beginning and end of a word that sounded "for all intents and purposes" like f**k during the 4pm show in school holidays.
It had been "purposefully edited to sound identical to the word f**k" and the programme had therefore breached the broadcasting code, Ofcom said.