The official threat level of an al-Qaida attack on the UK has been lowered today from "severe" to "substantial".

Terror threat level lowered

Terror threat level lowered

By Liz Stephens

The official threat level of an al-Qaida attack on the UK has been lowered today from “severe” to “substantial”.

The decision to lower the threat level follows a new assessment by the UK’s Joint Terrorism Analysis Centre (JTAC) on intelligence gathered on terrorist groups both within the UK and abroad.

“Substantial” is the lowest threat level the UK has seen since 9/11.

Speaking to the BBC on Sunday, the home secretary, Alan Johnson, acknowledged that swine flu is now considered to be a more imminent and realistic threat to the nation.

However, today Mr Johnson said in a statement: “We still face a real and serious threat from terrorists and the public will notice little difference in the security measures that are in place, and I urge the public to remain vigilant.

“The police and security services are continuing in their thorough efforts to discover, track and disrupt terrorist activity.”

Liberal Democrat home affairs spokesman Chris Huhne said: “There is no point in a graded early warning alert system if it only responds to events after they happen and if the public does not know the practical difference between the varying alerts.

“The centre should define its alerts by setting out some assessment of the probability of an attack over the coming year. The meaning of the alerts should be clear to the public or they should be junked.”

The system of threat levels is made up of five stages, although the difference between the stages has often been criticised as a confusing matter of semantics.

“Severe”, or level four, indicates an attack is regarded as ‘highly likely’, whereas “substantial” deems an attack to be a ‘strong possibility’.