Clarendon College in Nottingham has admitted it made a mistake in informing potential employees that an offer of work was conditional on joining the Education Lecturing Services agency.
The college, whose principal Pat Morgan-Webb has acted as an unpaid adviser to ELS, backed down after a would-be applicant complained that the advertisement had made no mention of any requirement to join the agency. However, when correcting the error it told the applicant that enrolling could broaden lecturers' "potential work opportunities".
The college's actions were condemned as "outrageous" by the lecturers' union NATFHE. FE negotiating secretary Sue Berryman said: "It looks to me like they are in the business of drumming up business for an agency when one would assume that is part of the costs of the agency."
The case has sparked renewed union concern over the way colleges use agencies. The union claims it has other examples of colleges choosing staff, then telling them to register with an agency.
In theory, colleges should approach the agency itself when they seek staff they do not intend to employ directly, giving details of the posts available and qualifications required.
The union claims institutions are having their cake and eating it by using agencies as a means of passing over responsibility for part-timers' sick pay and other costly employment rights, while also hand-picking the staff they want. However, ELS insists it has built in procedures to make such tactics impossible.
The Clarendon case arose after the college advertised in order to fill 10 "key posts", including an hourly-paid maths lecturer.
Dr Richard Skyers, a retired maths teacher, applied for details and an application form and received a covering letter stating Clarendon's policy of offering hourly-paid lecturing work first to existing employees and then to ELS-registered lecturers.
The letter gave the agency's address and phone number, adding "if you are offered work at Clarendon and you are not on our database it will be necessary for you to register with ELS".
Dr Skyers wrote back saying: "The element of compulsion does not equate with the equal opportunities policy you emphasise as having at Clarendon College, and I feel discriminates against anyone not wanting to register with ELS. "
The advertisement had led him to believe the successful candidate would be directly employed by the college, he told The TES.
Gill Northwood, director of human resources at Clarendon, replied to Dr Skyers and apologised for the "error" in the letter, implying the work was conditional upon ELS registration, and stating that the successful applicant would be employed by the college.
The reference to ELS was intended to "inform members of the community who may be interested in registering with them", she added. That information would "potentially enable a person to use this route to make themselves known to a number of colleges who use the ELS database".
No one was available for comment at ELS or Clarendon. The college could not confirm whether other applicants for the maths job had been informed of the error over the registration with ELS.
Roger Ward, chief executive of the Association of Colleges, said a new code of practice being devised by the AOC in conjunction with agencies would set out clear guidelines on the relationship between lecturers, colleges and third party providers of staff.