The University and College Union warned that plans for two-year "fast-track" degrees would damage the reputation of UK degrees and would lead to education being delivered "on the cheap".
The union's annual conference in Manchester voted yesterday against the introduction of the degrees, saying they would massively increase the workload of staff and reduce the amount of time they could spend carrying out research.
Delegates said squeezing three-year degrees into two years could not be achieved on the back of "swingeing cuts" to higher education and would have a "devastating impact" on the quality of students' experiences.
Karen Evans, from the University of Liverpool, said: "Accelerated degrees have no educational value and will stop students from having a well-rounded education. As well as placing a huge strain on staff it will also mean an additional burden on students, many of whom have to work through the summer to pay back the debts of tuition fees."
The union's general secretary, Sally Hunt, said: "Two-year degrees may sound great on paper but are in effect education on the cheap...Our universities are places of learning not academic sweatshops and we need to get away from the idea that more can be delivered for less.