The Home Office yesterday launched an investigation into whether a string of Scottish colleges with questionable credentials uncovered by The Herald are being used as an elaborate front for an immigration scam.

Its Border and Immigration Agency is to probe whether the colleges have been set up purely to bring immigrants into the UK under student visas, rather than to educate them.

In the wake of the move, Des Browne, the Scottish Secretary, said he was "obviously concerned" over any suggestion the UK's "robust immigration policies" had been compromised.

Last week, The Herald revealed a number of colleges based in Glasgow were advertising non-existent courses or were using logos of recognised educational and industry bodies on their websites without permission. Despite this, all the colleges were on an official government list which allows visas to be issued to students who have secured a place at them.

Two of the colleges, Commonwealth College Glasgow and Great Regent College, set up dubious websites which described lavish facilities and highly specialised courses, despite being based at a private flat and a rundown office block.

Another two institutions, Middlesex College and Glasgow College, which were unearthed yesterday, both have misleading website addresses registered in the Ascension Islands. Two of the colleges, and scores more operating throughout the UK, appear to be connected to an institution called Newcastle University, which is operating illegally in the American state of Oregon.

The Newcastle University website, which has no connection to the legitimate institution in the north-east of England, claims to have a UK base in Essex but its address is actually home to a private college called Abbey College, whose principal is listed as Mohammed Ali Raja.

The Abbey College prospectus has detailed information about the process for applying for a student visa and, under the heading "overseas consultants", contains a list of immigration agencies in Pakistan and India.

Yesterday, Umbreen Iqbal, the woman who runs the Commonwealth College, confirmed the institution used immigration agents on the sub-continent to recruit students. Middlesex College said they had opened a Glasgow branch specifically to capitalise on the Scottish Executive's Fresh Talent initiative, which allows successful students a visa extension when they finish their studies. Glasgow College also advertises Fresh Talent.

A source close to one of the colleges said last night: "It is all about immigration and getting a visa. I have seen it in Lahore where they hire out a function room in a hotel and give seminars on how to get into the UK through a college."

A spokesman for the Border and Immigration Agency said: "Institutions are visited on an intelligence-led basis and removed from the register where they are found not to be bona fide. A total of 45 colleges have been removed since 2005."