Government plans to cut the number of foreign students at universities and colleges will cost far more than they will save, according to the Home Office's own estimates.
Officials predict the clampdown, brought in because of fears that bogus colleges are allowing too many immigrants into Britain would cost the economy between £2.4 billion and £3.6bn.
The figures provoked an outcry among academics. Pam Tatlow, chief executive of the university think-tank million+, said: "Of course we should be doing more to crack down on bogus colleges but the system did not need the Government to take a sledgehammer to it. The end result could be a catastrophic loss of education exports."
The crackdown is part of Prime Minister David Cameron's drive to bring net immigration down from more than 200,000 a year to just tens of thousands by 2015.
The cost includes £2bn in reduced spending from students and their dependents who will no longer be able to come to the UK and work. A further £170m will come from cuts in fees income while £1.2bn will come from a cut in what students would have spent post-study.
However, the assessment by the Home Office adds that the move will save £1.1bn as well. There will be 273,000 fewer student visa grants and £840m savings in reduced costs for public services. "It may be there will be even greater benefits as it is not unreasonable to assume that jobs not take by migrant students will instead be taken up by British workers," said Immigration Minister, Damian Green.