Campaign groups are trying to stop the exploitation of the 15,000 postgraduates who teach in universities, who they claim are being used as cheap labour.
The University and College Union, the National Postgraduate Committee and the National Union of Students are urging universities to sign a charter promising postgraduates pay and treatment equivalent to full-time staff.
The groups will also send a booklet to every postgraduate to make them aware of their employment rights, as part of the campaign launched this week.
Simon Felton, general secretary of the NPC, said that some postgraduates were not getting proper training in teaching, were not paid properly or were not being allowed enough time away from teaching to do their own research.
Wes Streeting, NUS vice-president (education), said he supported the use of postgraduates in teaching as long as they were not "treated as cheap labour". But he added that they should not be "exploited as a substitute for well qualified and experienced staff".
Research published last month from the Higher Education Policy Institute showed that non-academics taught almost a third of seminars in old universities. Research for the UCU in 2005 found at least 15,000 postgraduates did hourly paid teaching in universities.
The Universities and Colleges Employers' Association said that any teaching that postgraduates undertook was "of clear benefit to institutions and provides postgraduate students with valuable work experience".
The spokesman said that the 3 per cent employed by their universities for limited periods "should, and did, receive appropriately equitable pay and benefits".
"The proposed charter fails to focus on postgraduates as students first and foremost. This charter needs to recognise that they are employed for a very small part of their time and that their responsibilities are very different from those of full-time, experienced employees," he said.