"They will be joined by convicted terrorists serving short sentences who, once freed, are likely to be just as committed to the cause of jihad as before they were jailed. This "new wave" will pose a significant challenge to the security services responsible for identifying and monitoring them," Clarke was quoted by The Telegraph as saying.
Pointing out a strategy change by the Al Qaeda, the security expert says that fundamentalist leaders are encouraging individuals to launch less sophisticated but equally deadly attacks on crowded places.
'Their targets have also changed from concentrating on aircraft to including attacks on trains, hotels and sporting events,' he said.
'British prisons still house more terrorists than in any other European country, though not for very long periods. Just 23 people, around 19 per cent of those convicted of terrorism offences, have been given life or indeterminate sentences. It is more likely that the majority of those released will remain as committed to their cause as before, and may serve as a source of motivation to others, albeit in clandestine ways.' Clarke, who was advisor to former British Prime Minister Gordon Brown, added.
The report cites estimates by prison probation officers that up to one in 10 Muslim inmates are being successfully targeted while inside jail, leading to the creation of a new generation of potential attackers who are due for release in the next decade and whose previous convictions do not relate to terrorism.
According to The Independent, all major sporting events such as this year's Commonwealth Games in India and 2012 Olympics in London should be considered as possible targets for this new generation of "lone killers" who have been radicalised by preachers in the hope that eventually at least one of their number will be successful.
Image: Abu Hamza, former preacher at London's Finsbury Park mosque, is in remand in the high-security unit of Belmarsh prison