Donny Osmond will be joining Strictly Come Dancing's judging panel for a special one-off guest appearance - and he has warned he will be a "tough judge".

For one week only, the star will join Len Goodman, Bruno Tonioli, Craig Revel-Horwood, and Darcey Bussell, as they cast a critical eye over the dancefloor this autumn.

Donny is no stranger to sequins and toe-tapping, having won Dancing With The Stars in America in 2009, when he beat Kelly Osbourne to win the coveted trophy.

He said: "I know what it's like to hold that trophy in your hand and believe me, it's worth all the blood, sweat and tears you put into your dances.

"I'm going to be a tough judge and the contestants are really going to have to give me their all."

Donny said being asked to be a guest judge was a "huge honour".

Louise Rainbow, executive producer of the BBC dance show, said: "Having won Dancing with the Stars himself, Donny knows what it takes to win that trophy and we all look forward to hearing his comments."

The singer first shot to fame alongside his brothers in the 1970s as part of The Osmonds.