"People think lecturers at this time of year are just sitting around waiting for Wimbledon, with plenty of time on their hands, but they are mistaken," said Paul Mackney, general secretary of the lecturers' union NATFHE.
His comments come as boards attempt to get principals to release lecturers on secondment to mark papers throughout June. The extra workload has been created partly by the overlapping of marking for A-levels and the first half of the two-year AS-levels.
"The boards have been trying to pass responsibility for marking onto lecturers since the 1970s," said Mr Mackney. "And what we are seeing is an attempt to get things done on the cheap."
If lecturers are released, he said, it should be those, including part-timers, who would otherwise not have work in colleges.
The forthcoming work-to-contract, which was agreed at the union's annual conference at the weekend, will not include a ban on marking. "But," he added, "the majority of colleges simply won't have the lecturers to spare."
David Linnell, principal of John Leggott Sixth Form College, Humberside, said he has advised his lecturers not to take up the offer after his college was approached by the Assessment and Qualifications Alliance.
"I told them that I found their request completely outrageous. My staff are contracted to work for the college, not for examinations boards. Even if I could release someone, I thinkthe governors would wonder what sort of college we are running if we can say 'yes' to our lecturers going off to work elsewhere.
"My main concern is that people need to be properly trained to mark papers and I worry about what quality of marking my students can expect to get for all the hard work they have put in."
The AQA says lecturers are experts at marking and understand the curriculum. It insists that some are able to take time out during the summer without damaging college business.
John Leggott college is one of the colleges approached by Marion Ashworth, principal subject manager of the AQA. She wrote to colleges, offering to pay them pound;120 a day for seconded lecturers from May 26 to June 25. This is less than they are paid by the college. Additional fees of around pound;3 a script are available.
A spokesman for the AQA said: "During this particular period, there are lecturers who would have previously been preparing students for their A-levels but are free. We would say the volume has increased by about 50 per cent because we have people who are doing the A-level examinations but, in addition, people who are being examined for what is effectively half an A-level.
"The marking will be to the usual high standards we would expect, bearing in mind that teachers are used to marking course work and are aware of what the examining boards are looking for."
The AQA says it has "not felt the need" to offer a bounty to teachers who can find colleagues to carry out marking. Edexcel is offering a pound;200 finders' fee to existing examiners.