A Midland college which is sacking nearly 500 staff and making them re-apply for their jobs is breaking the law, union bosses warned.
They have demanded Walsall College of Arts and Technology halt the programme or face a costly legal battle through the courts.
A total of 470 tutors are affected by the college's restructuring drive, announced just weeks before Christmas.
The programme, which is expected to include some redundancies, also features plans to scrap A-level provision and concentrate on vocational NVQs.
But college union NATFHE claims bosses at Walsall failed to adhere to legal obligations requiring them to consult staff, students and the community first.
A letter from NATFHE's lawyers which gave the college five days to withdraw its plans has gone unheeded, sparking the legal challenge.
Kevin Butley, chairman of Walsall College's NATFHE branch, said: "There has been no response from the college.
"It will now go to the next stage. Our solicitors are very serious about this and very confident the college hasn't done things properly.
"There was a 2005 case in the European Court and one in this country which set the precedent for this and which we would rely on."
Lawyers for the union plan to evoke the Trade Union and labour Relations (Consolidation) Act 1992 which calls for consolidation before restructuring.
"We don't believe there has been full and proper consultation about the redundancies and the course restructuring has been without consultation with the local community, the learners and the teachers," added Mr Butley.
The union says staff are being put through enormous stress before Christmas and those re-employed will find themselves on "inferior" contracts.
But Walsall College maintained it had been forced to implement the restructuring, which includes new contracts for lecturers, to achieve "value for money in the use of limited public funds".
It claimed A levels were being axed because they were not performing well and failing to meet the needs of the local community.
The measures are based on recommendations from consultants hired by the college following a review of the curriculum.
John Beaty, the college's marketing manager, defended the drive and claimed re-employed staff would be on better contracts.
"Walsall College is following all legal and due process relating to the curriculum review," he said.
"We maintain the opportunity for our staff to get enhanced salaries as a result of the staffing restructure that underpins this vital project."
But the National Union of Students also attacked the restructuring plans.
It said students half-way through their A levels would not be able to complete their studies. Regional NUT vice-president and Walsall College student Terri-Ann Lee Shung said: "This is terrible news for Walsall students.
"I am now unable to resit an AS level and am worried this will mean I won't be able to go to university.
"I am concerned both for myself and the many other students this will affect."