Changes to visa rules are set to bar thousands of foreigners from studying in the UK and cost colleges millions in lost income.
From next spring, non-EU students cannot apply to study in the UK for courses below level three (A-level equivalent), meaning dozens of popular lower level language courses and vocational programmes will be closed to them.
Colleges heavily involved in international recruitment say it will damage a growing area of business at a time when they are under pressure to seek new sources of income.
Catherine Vines, head of international operations at Ealing, Hammersmith and West London College, said it would lose 400 students and an estimated Pounds 250,000 as a result of the changes.
She said: "Vocational courses have been our biggest growth area. Students come here because they want to learn a skill that will get them a job. They are studying things like catering, hair and beauty, motor vehicle studies, which they just don't offer at home, because their countries have just opened up.
"Or they come to the UK because demand outstrips supply in places like Iraq, Iran and China where there can be 60 or 70 students in a classroom.
"For FE colleges, these courses are our core business. It's like saying they aren't valuable for an overseas student to do.
"But the UK government is asking colleges to diversify income and this is one sure way of doing it."
She said the decision would hand millions of pounds of business to other English speaking nations, particularly the US, Canada, Australia and South Africa.
The Home Office is concerned about bogus applications, but large, publicly-funded colleges that are already under close scrutiny were unlikely to support fraudulent claims, Ms Vines said.
There are about 84,000 international students at all levels in FE each year in Britain, worth around Pounds 60 million or the equivalent of more than three average-sized colleges. A further 40,000 foreign students at private colleges bring Pounds 260 million in fees.
Visa decisions are handled by entry clearance officers abroad, but the system has been criticised for being too idiosyncratic and subjective. From the spring, applicants will be rated on a points-based system to judge their likelihood of successful study or contribution to the workforce. Colleges will be expected to take on responsibility for informing the Home Office if students fail to enrol or drop out.
Publicly-funded colleges with a good track record of following visa requirements will be given a high rating and can expect applications to be successful, according to the plans.
The changes were made after consulting with the joint education taskforce, which includes representation from colleges. The Association of Colleges' response stressed that there should be a clear distinction between public sector colleges and non-accredited commercial centres.
A spokeswoman for the Home Office said: "The points-based system for managing migration will simplify the rules, ensuring that those who study here benefit Britain. That's why foreign students wanting to take advantage of Britain's world-class universities and colleges must meet strict criteria."