The 25 per cent cut announced by the David Cameron government will lead to over 22,000 jobs losses in universities and colleges, including over 10,000 academic jobs, the Universities and College Union said.
It warned that increased class sizes and less contact time with lecturers would make it a far less attractive place to study for overseas learners, who currently contribute 8.5 billion pounds to the economy a year.
Many Indian-origin academics in British universities are also likely to be affected by the proposed funding cuts.
"Do we really want to be left behind and risk being shunned by foreign students who will go to study elsewhere? We have a proud international reputation, but we realistically cannot expect to remain a major force in the global knowledge economy in the face of these cuts," UCU general secretary Sally Hunt said.
The union warned that a significant impact of the planned cuts would be on university students in some of the largest class sizes in the developed world.
Slashing university funding would have a devastating effect on the overall quality of students' experience at universities as another knock-on effect would be a huge reduction in vital support services, such as libraries and student counselling, UCU said.
The figures were conservative estimates and the impact of cuts on jobs and class sizes could be even worse, it said.
The union said its analysis raised serious questions about the country's future role as a leading player in the global knowledge economy.
"The scale of the cuts that we are facing is unprecedented and will have an undeniable impact on the student experience," Hunt said.
Lecturers that survive the cull will have less time to give individual students as they pick up the workloads of former colleagues and there will be fewer support services for students.
The government will effectively be asking students to pay for more for less at a time when our international competitors are investing in higher education, Hunt added.
Britain is currently the second most popular destination in the world for foreign students after the US.
The union said its analysis assumes that any cuts would be spread proportionately across staff and non-staff costs.
However, it may well be that variable costs, such as staff costs, take a bigger proportional hit than fixed costs.
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