Police chief Sir Ian Blair has refused to quit despite more criticism over the investigation into the shooting of Jean Charles de Menezes.

The Metropolitan Police Commissioner has been at the centre of an extraordinary political storm led by shadow home secretary David Davis and others who have repeatedly called for his head following the outcome of an Old Bailey trial relating to the case.

Earlier, in a long-awaited report, the Independent Police Complaints Commission (IPCC) said Sir Ian attempted to block the investigation into the shooting of the innocent Brazilian electrician at Stockwell Tube station in July 2005.

However, the police chief responded by saying he will remain in his job and is satisfied that his force has "significantly improved" procedures for dealing with life-threatening situations in the wake of the case.

He said: "Insofar as I have had sight of the report for over 18 months and have been well aware of its contents, its publication today makes no difference to the position I made clear yesterday - I intend to remain in this post.

"My reasoning is very simple - by the very nature of its task, the history of the Metropolitan Police Service is littered with controversial events. I don't need to repeat a litany of them now but every Commissioner has such events on his watch."

He said he had "deep and very personal regret" for the death of Mr de Menezes, adding: "The MPS has never sought to avoid accountability for the death of Jean Charles de Menezes. We killed an innocent man.

"Hardly a day goes by when I have not thought about how things could have been done differently and thus Mr de Menezes would still have been alive."

Earlier, the IPCC's chairman Nick Hardwick said Sir Ian tried to block IPCC investigators from the Stockwell scene, police officers and witnesses and is responsible for "much of the avoidable difficulty" caused after the tragedy.

The report also revealed that prosecutors considered and rejected murder charges against the two officers who fired the fatal shots.

Charges of gross negligence against Assistant Commissioner Cressida Dick, who was in charge of the ill-fated operation, were also considered and rejected, the report said.

It highlights a series of major failings, including poor communication between officers that led to Mr de Menezes being mistakenly identified as a wanted terrorist the day after a plot by would-be suicide bombers was foiled.

Much of the 167-page IPCC report formed the basis of the successful Old Bailey prosecution against the Met for health and safety breaches.

But it contained previously unpublished details about the police operation and the final moments of Mr de Menezes' life on board the Victoria Line train.

Speaking after the report was published, Mr de Menezes' family said the combined failures of the police made Sir Ian's position "untenable".

Vivian Figueiredo, a cousin of Mr de Menezes, said reading new details of his death was extremely emotional.

Speaking about Sir Ian's position, she added: "But we also believe that whether he goes or not will not mean that justice for Jean Charles' death will have been achieved.

"Until all those directly involved in Jean's death have been held accountable in a court of law we will not rest.

"We still believe there are other issues of why Jean was killed, why he was shot seven times in the head and why a shoot-to-kill policy was used."

On Wednesday, members of the London Assembly unleashed a wave of resignation calls after they passed a vote of no confidence in Sir Ian.

Tory members of the elected body said he must step down as the head of an organisation the Old Bailey judge said was behind "catastrophic" errors.

Sir Ian said he retains the support of senior politicians, his officers and the majority of Londoners.

And he has received the vocal support of Home Secretary Jacqui Smith, London Mayor Ken Livingstone and Police Authority chair Len Duvall.

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