"Brian and the bear", created by Cravens, sees Blessed crashing into a pub riding a Russian bear to break the news about the bookmaker’s latest World Cup match betting offer.
It concludes with the big-voiced actor delivering some weak puns and instructing his baffled audience to laugh.
It was created by Adam Johnson and Stephen Carroll, and directed by Damien O’Donnell through MTP.
The ad will be followed by further ads featuring celebrities including Kelly Brook and Inbetweeners star James Buckley. They will cover other sporting events including the new football season and horse racing.
Cravens was appointed by Ladbrokes in February following a competitive pitch. Ladbrokes said it was continuing to work with its previous agency, Big Al's Creative Emporium, on some creative work.
Alexis Zamboglou, marketing director at Ladbrokes, said: "Ladbrokes is a big, inclusive brand close to the hearts of all the nation’s bettors and gamers. Our new campaign not only promotes our great range of products, but is also a real ‘call to play’ to customers, existing and new in the homes, pubs and high streets across the land."