LEAF, the Lecturers Employment Advice and Action Fellowship, says that colleges continue to deny lecturers on part-time or term contracts their right to at least four weeks' paid holiday a year under the Working Time Directive.
Its claim stems from an employment tribunal hearing in July, when lawyers for the Assocation of Colleges conceded that colleges were "emanations of the state". This automatically made their employees subject to the terms of the directive.
LEAF has seen its support increase since the tribunal and now has members in more than 60 colleges. But its repeated requests for a meeting with further education minister Baroness Blackstone to discuss the matter have been turned down.
David Evans, LEAF's general secretary, said: "The fact is that even though the regulations are in place people are still not getting their entitlements. There are thousands in this category.
"We are hoping that the minister responsible will take appropriate steps to rectify this situation."
He said colleges were quite aware of the law but that some had been trying to avoid their responsibilities by asking new employees to sign contracts which expressly deny them paid leave.
The tribunal, a landmark case between lecturers and employers at Havering College in Essex, was adjourned after six days. When it reconvenes on December 13, it will decide whether, under the law relating to transfer of undertakings, lecturers should have maintained their Silver Book terms and conditions when colleges left local authority control and became corporations in 1993.
At the hearing, lecturers backed by LEAF won another crucial concessions from the college which was sponsored by the Association of Colleges, when it agreed that the change of control was a "relevant transfer" under the Acquired Rights Directive.
The tribunal decision, due early next year, is one of the most eagerly awaited in further education history. If LEAF succeeds colleges could face a bill of several hundred million pounds for backdated pay rises, holidays and for reimbursing additional workloads.