Beijing's plans for the London leg of the Olympic torch relay suffered a setback yesterday when it emerged that a number of torch-bearers, including the BBC's most senior journalist, have abandoned plans to take part in Sunday's event .

There was also confusion surrounding whether or not China's ambassador to Britain, Fu Ying, would participate in the relay. With protest groups opposed to China's human rights record preparing to stage mass demonstrations along the 31-mile route, the Chinese embassy denied reports that the ambassador had withdrawn. But embassy officials said the ambassador was required to spend the day with a Chinese government delegation accompanying the torch, leading to confusion as to whether she would take part or not.

In a later statement, the embassy said: "There has never been a view expressed from the Chinese embassy at any point that the ambassador is pulling out of the torch relay. She hasn't said that herself either."

Mark Byford, the deputy director general of the BBC, has also backed out of a commitment to carry the torch amid concerns that his participation would compromise the corporation's journalistic standards. Gabby Logan, the sports presenter, is also understood to have withdrawn, having initially been included in a provisional list of celebrity torch-bearers. She cited a clash with her Sunday morning radio programme. Her husband, Kenny Logan, is taking part.

Comedian Francesca Martinez also withdrew saying she felt that taking part would legitimise violence in Tibet.

She told Channel 4 News: "I was very honoured to be asked, and very honoured to represent the disabled community. I fully support the Tibetan cause and in a way I feel that, because of the mounting pressure and the ongoing violence in Tibet, that torch-bearers should turn down their role ... because I feel that is truly promoting and supporting the Olympic ideals, which are unity and world peace, and that doesn't include invasion of other countries."

Byford, who is second in command at the BBC, head of journalism across all networks and chair of the BBC's London 2012 co-ordinating group, provisionally accepted an invitation from the Beijing Olympic organising committee to carry the torch. With China's hosting of the Olympics an increasingly controversial subject he withdrew.

"Mark Byford did provisionally accept an invitation to carry the torch, but then decided that as head of journalism it would be inappropriate to take part," said a BBC spokesman. "The torch relay is a major story and Mark might be required to make an important editorial decision, so he decided it would be inappropriate to take part."

His withdrawal highlights the sensitivities surrounding the torch relay and Beijing's hosting of the games, and contrasts with the position of Sir Trevor McDonald, presenter of ITV's News at Ten, who will carry the torch.

The torch relay, which left Greece last week and will visit 21 countries en route to Beijing, was intended to be a marketing exercise that would promote China and the Olympics around the world.

Following a violent crackdown on protests in Tibet last month, and continuing unease over Beijing's support for Sudan's government, it has become a lightning rod for those opposed to the communist regime.

Protests are planned in several of the major cities on the relay route, with Sunday's journey through London expected to be among the biggest.

The Metropolitan police will launch a £1m security operation to ensure that the torch gets from its starting point at Wembley Stadium to the O2 arena in Greenwich unscathed. More than 2,000 officers will be on duty, with police cyclists accompanying the torch as it is carried by 80 runners on a route that passes through Piccadilly Circus, Trafalgar Square and Downing Street, where it will be greeted by the prime minister.

Commander Bob Broadhurst, who will be in charge of the operation, said that his officers would respect the right of protesters to demonstrate and assist those groups that contacted them.

Protesters who try to disrupt the passage of the torch could be detained until it has left London on Sunday night. If demonstrations should turn violent, the relay could be abandoned or rerouted at short notice.

"If we had thousands of protesters who turned rough then we may take a pragmatic decision to move round them or go straight to the O2, but we will not be battling through people who are determined to stop the relay," Broadhurst said.