British lawmakers voted Wednesday to ban glorifying terrorism, giving Prime Minister Tony Blair a badly needed victory on a measure he said was key to preventing future attacks.

The House of Commons approved the ban 315-277, sending it back to the House of Lords, which had struck down the use of the term "glorification."

The two houses will have to wrangle over the measure, which Blair's government argues is key to disrupting terror groups' recruitment efforts.

"People who glorify terrorism help to create a climate in which terrorism is regarded as in some way acceptable," Home Secretary Charles Clarke said in the debate before the vote.

"They help to persuade impressionable members of their audiences that they have a moral duty to kill innocent people, in pursuit of whatever political or religious ideology they espouse," he said.

Blair suffered a major Commons defeat on security last year and needed the win on glorification to demonstrate he had reasserted control over rebels in his Labour Party.

In November, lawmakers rejected his plan to allow terrorist suspects to be held for up to 90 days without charge.

British authorities have been taunted in recent years by clerics and other extremists who espouse militant views — including support for Sept. 11 — and attract widespread publicity.

The House of Lords had voted to remove the word "glorification" from the government's anti-terror bill and replace it with language that would outlaw describing terrorism in a way that encourages people to emulate it.

Blair argued that was not good enough.

"If we take out the word 'glorification' we are sending a massive counterproductive signal," he said in his weekly House of Commons question session, hours before the vote. "It is a word that members of the public ... know and understand and juries would understand."

A clear ban on glorification, he said, was "absolutely vital if we're to defend this country successfully."

The opposition Conservative Party opposed Blair's measure, saying it was poorly written and would accomplish little.

"Wouldn't it be better to have a watertight law designed to catch the guilty, rather than a press release law designed to catch the headlines?" said William Hague, the Tories' foreign affairs spokesman.

Conservative Dominic Grieve said the term glorification was too vague, "a concept hitherto unknown to our law and undefined."

The proposal was part of the government's anti-terror bill, which was drafted after the bombings on London's transit system in July that killed 56 including the suspected attackers.

The bill would also outlaw training in terrorist camps and encouraging acts of violence. Only the glorification provision and several other amendments were up for votes Wednesday, not the overall bill.

Blair argued the Lords' approach on glorification was too weak and said it could be interpreted to apply only to spoken words, not written ones. Grieve said later that the language Blair believed restricted the ban to speech could easily be changed.

Opponents say the ban would be dangerous and unnecessary, pointing out that extremists such as the radical cleric Abu Hamza al-Masri have been convicted in Britain under existing laws against incitement to murder and racial hatred.

Blair suggested police could have stopped al-Masri sooner if there had been a ban on glorifying terror.

Lawmakers were also voting on whether to renew contentious powers that allow some terrorist suspects to be detained indefinitely under "control orders" — strict conditions that resemble house arrest.