The BBC has apologised after weatherman Tomasz Schafernaker was caught making a rude gesture live on air.
He raised his middle finger after news presenter Simon McCoy jokingly said his forecast would be "100% accurate".
After realising he had been shown on screen, Schafernaker tried to cover up by pretending to scratch his chin.
"The News Channel presenter in the studio acknowledged a mistake had been made, and we apologise for any offence caused," a BBC spokesman said.
"Tomasz was not aware that he was on air, and whilst the gesture was only shown for a second, it was not acceptable."
During a joking handover, McCoy said: "Now we'll have the weather forecast in just a minute. Of course it will be 100% accurate and provide you with all the details you could possibly want."
After Schafernaker's gaffe, McCoy said: "Every now and again there's always a mistake and that was it."
The weatherman later wrote on his website: "Prior to a live weather bulletin, I made a gesture off camera joking with my fellow presenters and without warning the camera went live to the weather studio.
"I am very sorry for any offence that might have been caused by my actions."
The Polish-born weatherman began presenting on BBC South East Today in 2001 before joining national BBC outlets in 2006.
He made a public apology in 2007 after calling the Western Isles and the west Highlands "nowheresville" during a live weather broadcast.
He was also reduced to hysterics by an unfortunate rude slip of the tongue while trying to say "muddy site" during a BBC Radio 4 forecast last year.