Wish to award own degrees strains federation, says Tony Tysome.
A review of the role of the university and its relationship with member institutions is under way after Cardiff decided to award its own degrees and use its own title - instead of the "University of Wales, Cardiff" - once its merger with the University of Wales College of Medicine is completed next month.
Some Welsh vice-chancellors fear that Cardiff's move may have dealt a "fatal blow" to the 111-year-old federal university.
There are worries that other long-standing member universities that hope to gain degree-awarding powers, such as Swansea and Bangor, may be forced to follow Cardiff if they too want to establish an individual identity with their own titles rather than use the University of Wales prefix.
The Welsh Assembly confirmed this week that legislation does not allow an institution to use its own university title if it is a member of a federal university.
The University of Wales, which is the UK's second-largest degree-awarding body, has created a working group to consider how different types of institutions with different aspirations and degree-awarding powers can be accommodated under the federal umbrella. An interim report in due in October.
Lynn Williams, the university's secretary-general, said Cardiff's departure was a "regrettable loss", although he pointed out that it would maintain a link as an "affiliated" member.
He said: "It is the question of university title that is the key issue.
Others that decided to use their own title and powers would come up against the same problem. We need to come up with a more flexible set of arrangements to accommodate different types of members."
David Grant, vice-chancellor of Cardiff, said he thought other institutions were likely to quit the federal university unless a solution were found.
He said: "The University of Wales is undoubtedly helpful to the younger institutions, but it has a difficult role with the more mature ones that already have the ability to ensure quality. I think it has to accept that much more responsibility for quality and standards must lie with member institutions rather than try to centralise it within a federal model."
Richard Davies, vice-chancellor of the University of Wales, Swansea, said his institution was "reserving its position, depending on how things go with the University of Wales review". He said: "It is not clear yet whether Cardiff's leaving has dealt a mortal blow. But the University of Wales is a very powerful brand, and it is possible that Cardiff has made a mistake.
Many of us would be very disappointed to see the federation break up."
... as it backs off to claim all lecturers' notes