The prime minister has been warned that the Manchester murder of an anti-terror police officer is a "wake-up call" to the threat facing the UK.

Speaking after the death of father-of-three Stephen Oake during a raid connected to the recent Ricin find, Iain Duncan Smith warned that Britain must act to halt terrorists from "abusing the asylum system".

Conservatives have claimed that the latest terror arrests highlight the need for a crackdown on asylum seekers coming from states known to harbour terrorists.

"It is too early to comment on the detail of the police operation," said the Tory leader.

"But would the prime minister agree that the terror raid in Manchester is a wake-up call to the nation reminding us all of the threat that we now face?"

Paying tribute to murdered officer, Tony Blair told the Commons that the incident "reminds us that the threat that international terrorism poses here in Britain and of the need to take all the measures that we can to stamp it out in all its form".

"We have got to ensure that these groups of fanatics who have no compunction in taking human life, and who have no demands that any political system could possibly accede to, we have to make sure that they are defeated," he said.

Blair also defended the government's record on anti-terror legislation.

And he warned that "this scourge of international terrorism is not limited to this country".

"This is an international problem and we have to take every measure we can here but also every measure we can to co-operate abroad," Blair added.