A quarter of UK colleges who want to enrol overseas students have been denied a licence by the Home Office.
Institutions have to meet UK Border Agency standards before being allowed to sponsor international students under the UK's new points-based system.
About 460 have so far been rejected as not making the grade, out of 2,100 that accept international students.
Immigration minister Phil Woolas said "bogus" colleges were the "Achilles Heel" of Britain's border controls.
There has been a boom in overseas students coming to the UK in recent years, with tuition fees last year totalling £2.5bn.
The government says students from outside the EU "play a huge part in the UK's cultural and economic wealth".
But it is using its new points-based migration system to shut down "bogus colleges" that are really just a route into low skilled work.
International students will need to be accepted by genuine institutions before they can come here.
Officials estimate up to 2,000 "bogus" colleges will be forced to close because of the changes.
Speaking on a visit to Imperial College, London, Mr Woolas said he wanted to protect genuine universities and colleges which he said were essential for the economy.
But he added: "We want to expose those who are not genuine students who are using fraudulent college offers to come here.
"In my estimation abuse of the student visa has been the biggest abuse of the system, the major loophole in Britain's border controls.
"I believe that the new system will benefit major institutions, colleges and private universities, but the backstreet bogus college is being exposed."
A cross party group on balanced migration called on the government to reveal how many students were in the UK under false pretences.
In a joint statement, co-chairmen Tory MP Nicholas Soames and Labour's Frank Field said: "This is a worrying but not totally astonishing revelation.
"Given there are nearly a quarter of a million non-EU students in British higher education institutions, the question this poses is 'how are many are here under false pretences?'"
The launch of Tier 4 of the points-based system means students will also need to prove they have enough money to live on for nine months, down from 12 months in the original proposals.
Dr Sharon Bolton, head of international student support at Imperial, said she was concerned about bureaucracy in the new system.
The 17-page application form for existing students to renew their visas was now 55 pages long, she said.
And she said some scholarship students found the income requirements exceeded the amount they were given by the university.
She said: "The application form for those in the UK is a massive administrative burden for the students themselves, the universities that are dealing with it, and for the Home Office workers who are processing them.
"I don't see how that's not going to cause delays."
But she welcomed the effort to "weed out" colleges that are "illegitimate".
'Play by the rules'
The Association of Colleges said none of its members, which include general further education Colleges, Sixth form colleges and specialist colleges, had been rejected during the screening process.
Robert Russell, Association of Colleges Finance Development Manager, said: "Colleges are hopeful that the new sponsor register will prevent fraudulent institutions from abusing the immigration system in Britain."
Before reaching the UK, students need to prove they have a place at a licensed institution, that they can financially support themselves, and must provide their fingerprints to the UK Border Agency.
Colleges have to prove they are genuine education institutions and they will have to report students who are not attending their courses.
Home Secretary Jacqui Smith said: "These new measures make sure people who come here to study - and the people who teach them - play by the rules.
"This new tier of the points based system allows us to know exactly who is coming to the UK to study and crack down on bogus colleges."