Tony Blair today defended his Government's controversial policy of imprisoning foreign terror suspects without charge or trial.

The Prime Minister said he was mindful of the civil liberty concerns, particularly after nine Law Lords recently ruled that Britain's anti-terror provisions were not compatible with human rights law.

But he said that he was also aware of the threat to Britain. "It is very easy to become complacent about this," said Mr Blair, in an interview on the BBC Radio 4 Today programme.

"We still have an active terrorist threat in this country. I am not trying to alarm people by saying that. I am simply trying to say that we have a serious problem."

The House of Lords' ruling on December 16 was a blunt condemnation of the Government's anti-terror strategy, paving the way for a constitutional clash between the judiciary and Parliament.

By an overwhelming 8-1 majority, the Lords ruled that the human rights of foreign suspects held for up to three years without charge or trial had been breached.

Under human rights law, individuals are guaranteed the right not to be jailed indefinitely without due legal process - a provision echoed in the English legal tradition of habeas corpus.

These rights were suspended by David Blunkett, the then Home Secretary, in a unique opt-out from Britain's obligations to human rights, in response to the September 11 attacks. He then introduced emergency anti-terror legislation.

The Lords ruled that the Government's suspension of the fundamental right not to be detained without trial was unjustified because it was applied only to foreign terrorist suspects, and not British citizens. They added that it was disproportionate in terms of the threat to public security.

The Law Lords did not have the power to strike down the Anti-Terrorism, Crime and Security Act 2001, but they quashed the Government's opt-out from the European Convention on Human Rights as unjustified, and declared the sections of the Act permitting detention "incompatible" with human rights.

Their landmark ruling has put the Government under pressure to change the law and procedures in such cases.

Until now, Charles Clarke, who replaced Mr Blunkett as Home Secretary last month, has stone-walled on the Government's next move, maintaining that it will be up to Parliament to decide what to do.

Today Mr Blair entered the fray with a defence of the Government's stance. The Prime Minister defended his record on human rights, but said that he had to balance those rights, and the criticism from the Law Lords, against what he knew of the risks Britain faced from foreign nationals plotting terror acts against innocent people.

"The fear I have is what happens if the security services are telling us these people are a threat, we allow them to walk the street and then they end up killing large numbers of innocent people," said Mr Blair.

"I am not saying this is going to happen, I am simply saying that's the dilemma we face."

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