Metropolitan Police Commissioner Sir Ian Blair was told elected London representatives have no confidence in him today - but insisted he will not resign.
Members of the London Assembly repeatedly clashed with Sir Ian as they demanded to know why he would not step down over the death of Jean Charles de Menezes.
A vote calling on the Metropolitan Police Authority to sack him was carried after more than two hours of demanding and sometimes angry questioning.
The City Hall vote was led by Conservative members who have joined their national counterparts in rounding on the commissioner.
But Len Duvall, chairman of the Police Authority, said Sir Ian has his full support and remains the right person to lead the UK's largest force.
He confirmed that an extraordinary meeting of the police authority, where another vote of confidence would be held, will take place in the coming weeks.
While today's Assembly vote carries little weight, if Sir Ian was to lose the support of the Authority, Home Secretary Jacqui Smith may find her continued support of him impossible.
Mr Duvall said further criticism of Sir Ian is sure to erupt tomorrow following the publication of the Stockwell Inquiry by the Independent Police Complaints Commission (IPCC).
He said: "Even if he offered his resignation over Stockwell then I would not accept it."
Mr Duvall revealed that the closest Sir Ian has come to being forced to resign was after he admitted secretly recording telephone conversations with the Attorney General.
He said: "That was the closest we have come in all the years I have been chair of the Police Authority."
Association of Chief Police Officers president Ken Jones said: "The London Assembly has today further added to the unwise campaign to force Sir Ian Blair from his job.
"Those working in the police service will note that the debate largely overlooked the considerable successes of the Commissioner.
"Thanks to him and the Met, terrorist attacks have been intercepted, dozens of terrorists brought to book and many lives have been saved.
"Sir Ian's approach has made London a safer place to live and work in."
He added: "We note that the assembly divided largely along political lines.
"This is of great concern to those who police the capital in particular, and those who police the country more generally.
"Policing and politics make for a volatile mix.
"The prism of party interests is a flawed perspective from which to judge those who are called upon to make life or death judgments."Reuse content