Tomasz Schafermaker made the gesture at presenters Simon McCoy and Fiona Armstrong on the BBC News channel.
When he realised he had been caught on camera, he tried to cover up what he was doing by scratching his chin.
"Tomasz was not aware that he was on air, and whilst the gesture was only shown for a second, it was not acceptable," Sky News quoted a BBC spokesman as saying.
"The News Channel presenter live in the studio acknowledged a mistake had been made, and we apologise for any offence caused," he added. (ANI)