The Association of University Teachers (AUT) believes that cuts being considered by the school of medicine at Imperial College of Science, Technology and Medicine in London will damage the quality of teaching.
The college is looking at proposals to shed staff as a result of the merger between Imperial College, St Mary's Hospital Medical School, Charing Cross and Westminster Medical School and the Royal Postgraduate Medical School, Hammersmith.
The AUT says the college is trying to save money by sacrificing teaching staff and student support as it focuses on winning high research ratings.
A spokeswoman said: "At a time when the government is increasing the numbers of doctors available to the NHS, the quality of the teaching they receive is being put under threat by staff cuts."
She said the loss of teaching jobs would have a "major impact on small group tuition, problem-based learning and on the pastoral care of students, particularly those from disadvantaged backgrounds who often need extra support".
"The AUT is opposing compulsory redundancies and has been involved in negotiations to try to resolve the problem through voluntary means, but the college is threatening redundancies if sufficient volunteers do not come forward by 31 July," she said.
Consultation
The AUT says Imperial College is considering sacking 120 staff, including 60 teaching staff.
But a college spokesman said the number of redundancies that needed to be made had not been decided, and added that the college was doing everything it could to avoid compulsory redundancies.
He said every member of the academic staff within the school of medicine had been consulted about the job losses, and denied that the cuts would have a detrimental effect on teaching.
The Rector of the College, Lord Oxburgh said, said: "Even after restructuring, the Imperial College School of Medicine will have one of the most favourable staff/student ratios in the country.
"Imperial College expects its staff to be outstanding in both teaching and research - not one or the other."
The AUT lobbied a meeting of the senate of Imperial College on Wednesday.
The senate is to advise the college council on the proposals for staff cuts.