International students from India and other non-European Union countries, who contribute nearly 4 billion pounds every year in fees alone, are propping up UK universities' finances, according to data collected by The Guardian.
International students pay three times more than their British and EU counterparts in fees.
Thousands of students from India and Pakistan, however, have not been able to start their courses in British universities from September because of long delays in issuing students visas, prompting concern among vice-chancellors.
Britain introduced a tighter student visa system in March this year.
Education managers believe that if international students are not able to start their courses due to the delay in issuing student visas, it could lead to a funding crisis.
Professor Steve Smith, president of Universities UK, the umbrella body of British universities, said: "We are very concerned that significant numbers of students may not receive their visas in time to start their studies in the UK this year".
"We are in danger of sending out a message that the UK does not welcome international students. It is of huge academic, cultural and financial benefit to the UK for these highly talented people to come to our country," he said.
Many universities were trying to accommodate late arrivals but there will be cut-off points after which students will not be able to join their courses, Smith added.
In Pakistan, there is reportedly a backlog of 14,000 applications for student visas. Simeon Underwood, head of admissions policy at the London School of Economics, said, "The sector's main worry is the damage this will do to the reputation of UK higher education overseas, especially in the Indian sub-continent, and the knock-on effect this will have on university funding".
Officials, however, said tough checks were introduced for all those who had applied for UK visas.
"We have introduced tough checks for anyone applying for a visa to enter the UK, with applications checked for fraud and forgery, with individuals fingerprinted and checked against a range of watchlists," a home office spokesman said.
