A London university has been banned from teaching overseas students, leaving more than 2,000 undergraduates potentially facing deportation.
London Metropolitan University has had its right to sponsor students from outside the EU revoked, and will no longer be allowed to authorise visas.
Ministers have concerns over issues such as whether or not students are working instead of attending courses.
A task force has been set up to help students affected by the decision.
The UK Border Agency said it had "failed to address serious and systemic failings" identified six months ago.
As well as stopping the university, which has 30,000 students in total, from accepting new applications, losing the licence could also affect thousands of existing overseas students at the university.
The National Union of Students (NUS) said it could mean more than 2,000 students being deported within 60 days unless they found another sponsor.'Panic and heartbreak'
The university's Highly Trusted Status (HTS) was suspended last month while the UKBA examined alleged failing, preventing it from being allowed to recruit overseas students.
Immigration Minister Damian Green said London Metropolitan University had failed in three particular areas:
- More than a quarter of the students sampled were studying at the university when they had no leave to remain in this country.
- A "significant proportion" of checked files found "no proper evidence" that the mandatory English levels had been reached.
- Universities must know that students are turning up for their course and are not using a student visa to enter the country for work, but more than half of the records sampled suggested the university "just didn't know" whether students were turning up for classes or not.
A statement posted on the university's website on Wednesday read: "The implications of the revocation are hugely significant and far-reaching, and the university has already started to deal with these.
"It will be working very closely with the UKBA, Higher Education Funding Council for England, the NUS and its own students' union.
"Our absolute priority is to our students, both current and prospective, and the university will meet all its obligations to them."
Although there have been other suspensions, no other UK university has been fully stripped of its ability to recruit overseas students.
The NUS has contacted Prime Minister David Cameron and Home Secretary Theresa May to "express anger at the way that decisions have been made in recent weeks and to reiterate the potentially catastrophic effects on higher education as a £12.5bn per year export industry for the UK".
NUS president Liam Burns said: "This decision will create panic and potential heartbreak for students not just at London Met but also all around the country.
"This heavy-handed decision makes no sense for students, no sense for institutions and no sense for the country. This situation and the botched process by which the decision was arrived at could be avoided if international students were not included in statistics of permanent migrants."
Mr Burns added that UKBA "could very easily have said: 'Well London Met, if you're not capable of taking international students, you're no longer allowed to recruit any more" - instead of saying to all the current, legitimate students: 'You now have to leave the country'".Help for students
Universities Minister David Willetts has announced a task force to help overseas students affected by the decision, which will include UKBA and the NUS.
He said: "It is important that genuine students who are affected through no fault of their own are offered prompt advice and help, including, if necessary, with finding other institutions at which to finish their studies."
A UKBA spokesman said it had been working with the university since it identified failings six months ago, "but the latest audit revealed problems with 61% of files randomly sampled. Allowing London Metropolitan University to continue to sponsor and teach international students was not an option".
"These are problems with one university, not the whole sector. British universities are among the best in the world - and Britain remains a top-class destination for top-class international students.
"We are doing everything possible, working with Universities UK, to assist genuine students that have been affected."