Staff at Brunel University fear that increased teaching loads and less time for research could be the result of efforts to tackle a multi-million-pound deficit.
Vice-chancellor Chris Jenks said in a speech last month that the university was experiencing financial problems and would have to make efforts to save money.
Managers subsequently discussed proposals for a 2 per cent saving in staff salaries across all departments to address a £7.9 million deficit.
The University and College Union branch says it has been contacted by a number of its members with complaints about cuts to part-time teaching that could lead to extra teaching loads in the next academic year.
"Such changes could seriously affect time for research," the branch said.
A branch memo to members said a regional UCU representative had sent a letter to the university seeking "clarifications on the current planned policy Brunel has for discontinuing further employment of hourly paid lecturers, in order to aid cost savings in the present financial crisis".
It added: "This UCU inquiry also seeks details on the impact of extra teaching loads likely to fall on permanent staff who have lecturing duties where the part-time hourly paid lectures are no longer available."
A university spokeswoman said that Brunel was expecting to report an operating cost deficit of around £5 million for this financial year. "This figure is some £3 million less than the reported deficit of £8 million for the previous financial year," she said.
"In line with other institutions, Brunel is facing a shortfall due to rising costs and significant investments in infrastructure and research staff over the past four years.
"However, the university holds considerable cash reserves and is financially stable."
She said that a range of "efficiency measures" is being considered, but "there are no plans for redundancies, no redundancies have been made, and there have been no changes to our policy on short-term contracts".