Sixth-form colleges had kept apart from further education and tertiary colleges since incorporation in 1993 because they were very different in character. They had their own employers' forum which avoided the agonies of industrial action over new contracts for lecturers.
But the distinctions between different colleges have blurred as sixth-form colleges have moved away from being A-level factories and into new adult education and training markets.
A group of around 25 principals - members of both the Association of Sixth Form Colleges and the Association for Colleges - are now calling for a merger. After intense lobbying, they claim to have support from at least half the 120 sixth-form colleges and will put a merger motion to their annual meeting at the end of the month.
The sympathies of the Sixth-Form Colleges Association (formerly APVIC - the Association for Principals of Sixth-form Colleges) are much closer to the AFC than to the Colleges' Employers' Forum. Many members blame CEF chief executive Roger Ward's management style for the protracted industrial action and strikes.
A merger would undoubtedly increase AFC chief executive Ruth Gee's power base in the wider merger talks with the CEF. Extensive enquiries by The TES suggest there is a close balance of support for the two in the AFC-CEF merger talks.
Nick Brown, principal of Oldham College and one of the 25, said: "If there is a unified group of the AFC and the CEF, and then another group of 120 in the sixth-forms association, who do people think ministers will listen to, us or them?" Many principals are concerned that sixth-form colleges would lose their identities altogether in a merger. But Ed Elvish, principal of Barrow-in-Furness Sixth Form College, disagrees. He has helped form a sixth-form working group within the AFC to try to bring the two organisations even closer.
"Whilst there are characteristics which will lead to particular challenges and opportunities for sixth-form colleges in the future, the common issues facing all FE sector colleges are greater than those which might divide us."