Lord Falconer

The House of Lords has once again defied government calls for it to back down and pass the Prevention of Terrorism Bill.

After the fourth debate on the issue in the upper house within 24 hours, peers rejected Tony Blair's warning that they were putting national security at risk.

The Commons and the Lords remain divided over two key issues - the burden of proof needed to issue a control order and whether or not the Bill should automatically expire after 12 months.

After a session of parliamentary ping pong which continued through last night, peers voted by 176 to 128 in favour of a move to raise the burden of proof required against suspects.

They also re-inserted the 12 month sunset clause by 194 votes to 123.

Both options had been rejected in votes by MPs just hours earlier.

Ahead of the Lords votes, the constitutional affairs secretary had said it was time for the unelected second chamber to back down.

"The time has come to respect the supremacy of the Commons, put aside our disputes on the debate, and join together to fight the terrorist threat that we revile," Lord Falconer told peers.

Home secretary Charles Clarke has refused to offer any more concessions on the two remaining sticking points.

The government now appears ready to let the bill fail and take the issue to the general election.

The Liberal Democrats confirmed they would continue to insist on the amendments even if it caused the Bill to fail.

A Conservative spokesman said the party still hoped for an agreement.

'Messing about'

Earlier the prime minister blamed the Conservatives for preventing police and security service advice from becoming law.

He said it was time for the Tories to "stop messing about" with the controversial legislation.

"We need to make sure that this country is properly protected against the terrorist threat," Blair told the BBC.

"This legislation is necessary to do so. It is in my view quite extraordinary, unbelievable, that you have the government trying to introduce the measures, the police and security services wanting to protect this country and the Conservative Party trying to do everything they can to water it down and frustrate it."

The prime minister said he "could not have a situation" where vital laws were not implemented.

He added that it was "absurd" for the legislation to be ping ponging back and fore between the houses of parliament despite the concessions the government had made.

Blair warned that there was "a genuine terrorist threat" to the UK.

"The security services and the police are advising us that we need these powers to defeat those who are planning and plotting terrorist activity in our country," he said.

"They want them on the statute book. They don't want them taken off the statute book."