An early version of Blue Peter's distinctive theme music

The head of BBC children's programmes, Lorraine Heggessey, said: "It is sad that such a talented presenter as Richard Bacon has not only let himself and his colleagues down but, most important of all, he has let down the millions of children who watch Blue Peter."

The sacking happened hours before the programme, which had just celebrated its 40th birthday, was the special award winner at the third British Academy Children's Awards in recognition of its "outstanding contribution to children's television".

BBC management is determined to protect Blue Peter's name

Richard Bacon, 22, of Chiswick, west London, told the News of the World: "I have been stupid and regret making a silly mistake experimenting with drugs.

"But I have learned the lesson the hard way and I hope it serves as a lesson to lots of other young people. I would also like to apologise to all loyal Blue Peter viewers."

Ms Heggessey added: "For 40 years, Blue Peter has been a force for good, providing positive role models for children to follow and helping them to become responsible and caring adults. It is vital that nothing tarnishes that reputation.

"Richard accepts that he left us no option but to terminate his contract immediately.

"He regrets his actions and has apologised to the Blue Peter team and to all Blue Peter viewers."

Mr Bacon apologised to viewers in a statement released through the BBC.

He said: "I fully accept and agree with the decision that has been taken.

"I regret what I did but it was in my personal time and I therefore hope that it does not reflect on the show.

"I am very grateful to Blue Peter for the opportunity it has given me and am very sorry that I have let everybody down."

Previous controversies

• In 1980 viewers learned that presenter Peter Duncan had once featured in a porn film.

• There was also controversy in 1985 when video of presenter Michael Sundin emerged showing him in his underpants with a male stripper at a London nightclub.

• Daniel Scott was "adopted" by presenters John Noakes and Valerie Singleton in 1968 and became the Blue Peter baby when he was aged 14 weeks. He made regular appearances on the show until he was two. It was later revealed that he had dropped out of school and took drugs.

• In 1987 controversy surrounded the revelation that presenter Janet Ellis was an unmarried mother.