The death of an innocent Brazilian man shot by marksmen of Scotland Yard's ant-terrorism squad in the summer of 2005 resulted from "very serious but avoidable mistakes," an independent report said Thursday.

Jean Charles de Menezes, who was shot seven times in the head by anti-terrorist officers who mistook him for a suicide bomber, fell victim to a series of failures in communication, planning and execution of the police operation, the report by the Independent Police Complaints Commission (IPCC) said.

De Menezes, 27, was shot on July 22, 2005, a day after police in London foiled an attempted second suicide bombing on the transport network, following the major attack of July 7, in which 52 people died and more than 700 were injured.

The Brazilian died after being followed by plain-cloths officers who chased him on to an Underground train at Stockwell Tube station in south London on the morning of July 22.

In its report, the IPCC said that police radios used on the day failed to work underground, and there was a "lack of clarity over language used by firearms officers and their superiors to sanction the shooting."

The police watchdog, which made 16 recommendations, demanded a "wider public debate and understanding of the tactical options for combating the threat from suicide bombers."

But in a passage likely to damage further the standing of Ian Blair, head of Scotland Yard, the IPCC said the police commissioner had personally been responsible for "delaying an independent investigation" into the shooting.

Blair, 54, who is under pressure to resign over the case, Thursday again expressed his "deep personal regret" for the "tragic" shooting of de Menezes, but made clear that he intended to stay in his post as Britain's most senior policeman.

"Our overall record is good. All the officers involved have my full support," he said. Blair again stressed the "difficult circumstances" in which the police were operating as London faced an "unprecedented threat" from terrorism.

Blair said London police had been called to 10,000 potential firearms incidents over that last 12 months, and fired "only three times."

While both opposition parties, the Conservatives and the Liberal Democrats, have called for Blair to step down, the Labour government of Prime Minister Gordon Brown has repeatedly expressed "full confidence" in the police chief.

The family of de Menezes welcomed the report, but said they would continue their efforts to achieve "justice" as no individual had so far been held to account for the shooting.

Spokeswoman Yasmin Khan said the report was "another damning indictment of the Metropolitan Police," while Blair's position had become "untenable."

The family's lawyer, Harriet Wistrich, said they would take the case to the European Court for Human Rights over "fundamental issues about the accountability of police officers who kill people."

Within hours of the shooting, Blair told a 2005 news conference: "This shooting is directly linked to the anti-terrorist operation."

Blair has said that he left his Scotland Yard offices late on the night of the shooting and was not told "until the next day" that an innocent man had been killed.

The IPCC, which demanded a public debate over the "policy to shoot suspected suicide bombers," said in its report: "The commissioner attempted to prevent us carrying out an investigation."

The victim's family described that statement as "shocking new evidence."