Colleges could be closed for almost a week in the run-up to exams by staff striking over low pay and pension changes.
Natfhe, the lecturers' union, has decided to strike after staff were offered a pay rise of only 1.5 per cent - a wage cut in real terms.
The two-day walk-out would take place on May 2 and May 3. Further strikes over pensions could close colleges for most of that week, although a Unison spokeswoman said talks were continuing and a strike was not certain. Barry Lovejoy, head of colleges at Natfhe, said employers had "scorned" offers to phase in pay rises to make them more affordable.
The union says the pay gap with school teachers is growing wider each year, and criticises colleges for not fully implementing pay agreements from two years ago. "We have no option but to send out a robust response that college staff will not be ignored," Mr Lovejoy said. "This will be the start of a programme of escalating industrial action up to and including indefinite strike action."
Colleges criticised the timing of the strikes, saying the union should have allowed negotiations to take their course.
Sue Dutton, deputy chief executive of the Association of Colleges, said:
"AoC is very disappointed that Natfhe have decided on this premature and disruptive course of action so early in negotiations, after just one meeting of the National Joint Forum."
She said talks were due to resume on May 10 and that the association was still consulting colleges about its offer. "Contrary to Natfhe's claims, AoC and member colleges are very conscious of the impact of pay on colleges' ability to recruit and retain good staff," Ms Dutton said.
Five other unions also rejected the 1.5 per cent offer, including Unison, the TGWU, the GMB and the Association for College Management.
Peter Pendle, general secretary of the ACM, said they had no plans to strike but refused to criticise the lecturers' decision, saying that the AoC had made little effort to compromise. He said: "If we are not very, very careful we are going to end up in a situation where national negotiations will deteriorate and break down."