Academics have raised concerns that the introduction of more private universities could damage the UK's global reputation for higher education.
Many are concerned that degrees offered by for-profit universities could be seen as inferior by employers.
A poll of 500 professors, conducted by the University and College Union (UCU), found that more than four in five (81%) believe that the expansion of private, for-profit universities would lead to a decline in the global reputation of UK higher education.
More than three-quarters (79%) thought employers would view qualifications offered by private universities as lower quality than those offered by other institutions.
Four in five professors (80%) said for-profit institutions should not be allowed access to state subsidies, and 88% disagreed with any relaxation of regulations that would allow private universities great access to public funds.
Two-thirds of those questioned said that for-profit institutions should be more tightly regulated than existing universities, with 99% saying these institutions should provide the same amount of information to the public as their state counterparts.
And 93% said that for-profit universities should have the same obligations to recruit more poor students as public institutions do.
UCU general secretary Sally Hunt said: "The findings of this report should act as an urgent wake-up call to ministers. Some of this country's most senior and respected academics have delivered a damning verdict on expanding the for-profit sector.
"If the Government ignores these warnings, millions of students face being ripped off by private operators whose main interest is their own profits, not education. For-profit providers are not the answer to the current funding crisis in higher education."
The Government is attempting to open up higher education to allow more private universities to operate, saying they want to make it easier for UK students to attend these institutions.