Warning over pressure on Blair

Allowing Sir Ian Blair to be "driven out" by media criticism over the Stockwell tragedy could render the job of Britain's top policeman "worthless", according to Mr Livingstone.

He insisted that both the Government and other senior police officers were "determined" Sir Ian would stay.

The intervention came as pressure built on the Met chief after he was personally criticised by the Independent Police Complaints Commission for holding up an investigation into the shooting dead of Jean Charles de Menezes.

The force was also found guilty at the Old Bailey of breaching health and safety rules in the botched operation, during which the innocent Brazilian was mistaken for a would-be suicide bomber.

Mr de Menezes' family have called for Sir Ian's resignation, and the Tories and Liberal Democrats have added their voices to the clamour. However, Home Secretary Jacqui Smith has repeatedly insisted she has full confidence in the commissioner, while Prime Minister Gordon Brown went out of his way to praise his "creditable" achievements.

In an interview for BBC1's Andrew Marr programme, Mr Livingstone said he had been in regular contact with ministers and senior police.

"We are all pretty determined we are not going to have a media campaign drive a commissioner from office," he said. "Other senior officers from around the country have been saying to Ian Blair, if you go the job will be worthless to your successors.

"They will spend their entire time worrying if the press is going to get upset. We have never had that before and we cannot allow it."

Mr Livingstone insisted the commissioner had to be independent both of politicians and of the media. "He is legally independent and we want to preserve that," he added.