Colleges stand to save Pounds 50 million after part-time lecturers were defeated in a long-running test case over pension rights.
Principals celebrated this week after the Court of Appeal imposed tight limits on the rights of public sector lecturers, teachers and other part-time workers to claim back payments for pension contributions.
But celebration may be premature as union leaders are to take the case to the House of Lords to secure a European ruling on the issue.
College employers launched the case two years ago after a European ruling that part-timers were entitled to the same pension rights as full-time staff.
Thousands of part-time lecturers are among the teachers and other public sector workers who have since bid for their employers to make up pension contributions over their years' service. But employers argued there should be a time limit on back payments, and last week the Court of Appeal agreed.
Judges ruled that part-timers could only apply for two years' back contributions. And they said part-time staff on fixed-term contracts, which covers many lecturers in FE colleges, had to apply for back contributions within six months of each contract ending - severely limiting claims.
Association of Colleges director of professional services, Marcia Roberts, said the appeal court ruling was "an excellent result for FE colleges and a result for common sense".
But Sarah Veale, of the TUC's legal team, said: "It's bad news. The unions had a meeting and there's very much a will to take this further so we are going to be petitioning the House of Lords."
The test case followed a ruling by the European Court of Justice that excluding part-timers from pension rights could constitute indirect sex discrimination, given that most are women.
At issue was the right of part-time lecturers to be allowed entry into the teachers' superannuation scheme, backdated to 1976, when sex discrimination legislation was introduced.
The case was initially taken to an industrial tribunal, before going on to the appeal tribunal and now the Court of Appeal.
Lawyers expect a year's delay before the case reaches the Lords, but part-timers will have their individual cases frozen until the issue is resolved.