At least two of the men suspected of being members of an alleged al-Qaeda cell had been allowed to stay in Britain despite allegedly breaching the conditions of their student visas, The Daily Telegraph has learnt.
One man was stopped by immigration officials at Manchester Airport last week as he arrived from Pakistan, but was allowed to enter the country despite his visa documents being "all over the place", according to one source.
Another suspect was threatened with deportation after immigration officials discovered he was working as a security guard instead of studying, but he was nonetheless allowed to stay.
(Article continues below)
The revelations will intensify pressure on the Government to carry out a complete overhaul of the student visa system after it emerged that all but one of the 12 suspects being held on suspicion of plotting an "Easter spectacular" bombing campaign had come to the UK from Pakistan on student visas approved by the Home Office.
Patrick Mercer, the chairman of the parliamentary counter-terrorism subcommittee, described the UK Border Agency's failure to act as "a disgrace" and a "frightening" lapse of immigration controls.
There were also calls yesterday for greater co-operation between the UK and Pakistan in vetting applicants for student visas, with Pakistan's high commissioner suggesting vetting procedures were currently inadequate.
