Jean Charles de Menezes' family has cast doubt on the findings of the Independent Police Complaints Commission (IPCC), claiming it is "inconceivable" Sir Ian Blair did not know Mr de Menezes was innocent until the day after his shooting.
If this was the case, Sir Ian was not in control of his officers, his family said. Alternatively police officers have conspired to protect the Met commissioner.
The IPCC report into the immediate aftermath of Mr de Menezes death on July 22 found counter-terrorism chief Andy Hayman deliberately misled the public and Sir Ian, but cleared the Met commissioner of any wrong doing.
Sir Ian has maintained he was not aware of Mr de Menezes' innocence until 24 hours after his death.
Speaking for the de Menezes family today, lawyer Harriet Wistrich said: "It is inconceivable that Ian Blair was not informed about the mistaken shooting of an innocent man until the next morning."
Ms Wistrich pointed out that a wealth of other individuals knew of Mr De Menezes' identity on the day of his shooting, including government departments and officers in other police forces.
She continued: "It seems inconceivable Sir Ian Blair did not know that. And if he really, really did not know it raises an equally shocking question about how someone in charge of the Met police could have been kept out of the picture of what was one of the most embarrassing moments in the history of the Met police.
"Either there has been a wide scale conspiracy to cover up the fact that Blair did in fact know and that all sorts of officers have been giving misinformation to this inquiry, or that there's just an absolutely shocking lack of command that so many people could conspire or failure to inform him."
Sir Ian sought to defend himself this afternoon. He denied there was anything amiss in his ignorance on July 22, maintaining he was preoccupied with the ongoing manhunt for the four failed suicide bombers from July 21.
He insisted: "My position was not unreasonable and senior colleagues did not let me down."
But he conceded the Metropolitan Police Service had suffered communication problems and said measures had already been taken to reduce these. "The Met has learned from what happened," he said.
Sir Ian welcomed the IPCC's finding that complaints made against him were unjustified.
"Despite much speculation to the contrary I did not lie to the public," he said.
The de Menezes family remain dissatisfied that misinformation was allowed to circulate in the immediate aftermath of the shooting.
Ms Wistrich suggested that "again and again" when someone is killed by the police, information is put out to suggest they in some way "invited the police to act in that way".
She also raised questions about the future of deputy commissioner Mr Hayman, who was roundly criticised in the report.
While condemning Mr Hayman's behaviour, the IPCC said it was the Metropolitan Police Authority's (MPA) decision to proceed with disciplinary action.
Ms Wistrich pointed out the MPA has been intimately involved in the investigation and questioned their ability to impartially respond to Mr Hayman.
Speaking after the IPCC report, MPA chair Len Duvall sidelined the criticisms levelled at Mr Hayman.
Mr Duvall said he was confident the MPS as a whole had learnt lessons from the "tragedy" and a number of the IPCC's recommendations had already been implemented.
Local MP Simon Hughes, however, said Mr Hayman could not keep his position and retain the confidence of Londoners.
The Liberal Democrat MP said the report raised serious criticisms of the management of the Met, all the way up to the highest level.
"The grave threats and pressures at the time do not justify the serious failures in the internal and external communications following the fatal shooting of Mr de Menezes," he added.