BBC bosses have accused Konnie Huq, the Blue Peter presenter, of threatening the impartiality of the programme after she defied the corporation by sharing a platform with Ken Livingstone.

The BBC has been forced to apologise to the Conservatives after she appeared with the Labour Mayor of London at a media event that Mr Livingstone used to attack his political opponents.

Mark Byford, the BBC Deputy Director-General, has apologised to Brian Coleman, the deputy chairman of the London Assembly, over the behaviour of Huq, 31, who has been a Blue Peter presenter since 1997.

Next year Mr Livingstone intends to run for a third term as mayor.

The BBC had turned down an “unsuitable” request for her to appear alongside Mr Livingstone to endorse the Hovis London Freewheel, a cycling event.

But, at her agent’s behest, she did so anyway. The mayor and Jenny Jones, a Green Party assembly member, used the event to accuse the Conservatives of pursuing “pro-car” policies.

Mr Coleman, a Conservative councillor, said: “The launch became a political rant. It is unforgivable for the BBC to allow the Blue Peter name to be lent to a political event. But when a presenter does so without their permission you wonder what is going on at the BBC.” Mr Byford said that the BBC shared Mr Coleman’s concerns and promised to “avoid anything similar happening again”.

In a letter to Mr Coleman, seen by The Times, Mr Byford wrote: “The BBC had turned this \ down on the grounds that it would be unsuitable for her and Blue Peter.

“It was felt that the BBC and the programme should not be linked with anything that might be construed as campaigning, and that this campaign potentially fell into that bracket.”

According to Mr Byford, Jonathan Shalit, Huq’s agent, “read her contract differently and booked her into it without the knowledge of the BBC”.

The BBC is now contacting all presenters and their agents to clarify “exclusivity clauses” that allow star names to earn lucrative freelance fees for public appearances.

Mr Byford said that the BBC must have an “absolute veto” over outside work undertaken by presenters. This applied to Ms Huq as a “public face of the BBC”. Huq has now withdrawn her support from the cycling event next month.

Mr Shalit said: “This was an entirely non-political event about helping to get Londoners cycling, and that is why I recommended that Konnie take part.

“Mr Coleman should concentrate his efforts on finding a political alternative to Ken Livingstone rather than attacking a presenter who just wanted to support a fitness campaign.”

Huq plans to leave the show next February when she will surpass Valerie Singleton’s record to become the longest-running female presenter of the show, which celebrates its 50th anniversary next year.Mr Coleman said: “I don’t think Valerie Singleton would have got herself into this mess.”

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