The shooting dead of Jean Charles de Menezes during a hunt for terrorists amounted to "a state execution", a leading Liberal Democrat has said.
Mr Menezes was shot a day after the failed London bombings
Matthew Taylor, the party's former chairman, said the "fundamentals of civil liberties" were under threat from government-led anti-terror efforts.
Mr Menezes was shot dead at Stockwell tube station the day after the failed 21 July bombings in London.
Mr Taylor said the government should not "surrender" the rule of law.
He told a fringe meeting at the Lib Dem conference in Blackpool: "I'm not prepared to stand by in a country that takes the decision to allow state execution on the basis of suspicion - even suspicion of mass terrorism."
Mr Taylor said: "I would not be convinced if there were five dead terrorists and one innocent man dead.
"We cannot defend the principles of this democracy and rule of law and liberty on the basis that we surrender them - even in the case of terrorist threats."
The chief commissioner of the Metropolitan Police, Sir Ian Blair, has described the policy of shooting suspected suicide bombers as the "least worst option".
However, he would not confirm to MPs last month whether Mr de Menezes had been killed through a "shoot to kill" policy.
But he said policy had been reviewed following the incident at Stockwell Tube station, when Mr Menezes was mistaken for a suicide bomber and shot seven times.
At the Lib Dem meeting in Blackpool, Mr Taylor criticised anti-terror legislation put forward by the government.
In particular, allowing the detention without charge of suspects for up to 90 days was wrong.
Mr Taylor said that even two weeks would be too much.
It was a time to show "strength" to defend civil liberties, he added.