Tony Blair last night insisted he was "101 per cent" behind the decision to launch an anti-terror raid on a house in east London last week.
One man was shot in the dawn operation, which involved about 250 police officers, and has subsequently been arrested. His brother is also in custody, although both deny being involved in terrorism-related activities.
Scotland Yard said the raid was based on "specific intelligence", thought to involve a chemical device of some sort, but it is coming under pressure to explain its actions after failing to find any evidence to support this, despite five days of searching.
However, last night the prime minister, who was on holiday during the raid but was kept informed, insisted the police had a duty to act on intelligence received about possible terror activities.
"I think that we should be very, very wary of drawing conclusions, but my view is absolutely clear," he said.
"I support the police 101 per cent, and the security services. I think that if they had a reasonable piece of intelligence that they think they have got to investigate and take action on, they should."
Metropolitan police assistant commissioner Andy Hayman said on Monday that officers had "no choice" but to act on the intelligence they were given, but Muslim leaders have warned that the raid threatens to undermine trust between the community and police.
"People want to know what exactly happened and about the intelligence - is it genuine information, is it flawed? These are the questions police have to answer as soon as possible," said new head of the Muslim Council of Britain Muhammad Abdul Bari.
But Mr Blair rejected suggestions of a backlash among British Muslims, saying: "It is a real mistake to think that your average person from the Muslim community is any different to anybody else.
"They know perfectly well there is a problem. We know there is a problem with terrorism - we are coming up to the July 7th anniversary."
He added: "You can only imagine if [the police] fail to take action and something terrible happened what outcry there would be then."