Much stricter regulations for student visas are trying to stop bogus colleges
Immigration Minister Phil Woolas is promising to "act swiftly" against any breaches of tough new rules to stop the misuse of student visas.
It follows an investigation in The Times claiming that a network of bogus colleges had been selling entry to the UK under the cover of student visas.
Thousands of people are believed to have used this illegal route.
"The UK Border Agency is systematically vetting colleges to clamp down on abuse of the rules," said Mr Woolas.
Concerns over bogus colleges have prompted the introduction of a much tougher inspection system for institutions wanting to recruit overseas students and sponsor them for student visas.
The investigation in The Times, focusing on a college in Manchester, highlighted claims that students, particularly from Pakistan, had been misusing the visa system to enter the UK.
It claimed that colleges were allowing many more students from overseas to gain visas than were really being taught.
Eight Pakistani men arrested in an anti-terror operation earlier this year were students at one of these colleges.
Certificates from bogus colleges were subsequently used by several students to enter for courses at legitimate universities.
Mr Woolas said that "this alleged fraud took place under the old system, and highlights exactly why I have brought forward changes which crack down on abuse of the student route into the UK".
This crackdown has seen the introduction of a more thoroughly vetted accreditation scheme for colleges and closer scrutiny of individual students, including the requirement for biometric identity cards.
It follows widespread concerns about the lucrative trade in bogus colleges operating as covers for student visa fraud - described by Mr Woolas as "the major loophole in Britain's border controls".
About a quarter of colleges applying for registration have been rejected - and so far no colleges which have been accredited have had this status withdrawn.
There are currently about 1,500 public and private educational institutions which are allowed to sponsor overseas students.
And the immigration minister has promised to maintain a tough stance if there are signs of fraud under the new tighter regulations.
"We will act swiftly where there is credible evidence of organised abuse of the immigration system by any college - registered as a sponsor or not," said Mr Woolas.