Plans to give academics at the University of Warwick more annual leave than their non-academic colleagues have been criticised by the trade union Unison.
The issue has arisen as part of the movement of academic and non-academic staff on to a new single pay spine, under the 2004 national framework agreement reforms.
In a statement issued in the summer, human resources director Michael Blair says: "The ballot process (to agree the reforms) has been delayed due to a very late intimation from Unison, whose central office consider that the proposed annual leave entitlements are potentially discriminatory on grounds of gender ... the university has sought further legal opinion and we remain of the clear view that no such discrimination exists."
Times Higher Education understands that the human resources department analysed the gender balance of all staff in pay grades five to nine and found that there were no more women among the non-academics than academics.
The university also argued that giving the same holiday to all staff would be too expensive, although Unison said that equal holiday entitlement could be phased in to mitigate the cost.
Unison said it had concerns over the fairness of the leave differential as well as its legality.
Jon Richards, senior national officer for education at Unison, said: "Grade-related differential leave is not good practice - so to make it worse by occupational segregation goes against the trends of modern HR. It is also certainly against the principles of the framework agreement, which was designed to bring the different grading structures and some national conditions together - subsequent related advice (some of it from the Universities and Colleges Employers Association) has made it clear that terms and conditions need to be harmonised to meet equal-pay considerations."
Grade-related leave had been abolished in pay modernisation deals agreements in health and local government, he added.
At recent seminars on pay modernisation, speakers highlighted the risk of equalities challenges in connection with differential conditions of service, Mr Richards said.
The University and College Union, representing academic and academic-related staff, backed a phased introduction of equal annual leave, provided that academics did not have their own entitlement reduced.
About 10 per cent of institutions, including Liverpool John Moores University and the University of York, have harmonised leave for all staff on all grades.
Most universities have given academics and non-academics in higher grades the same amount of annual leave, while offering support staff in lower grades reduced holiday.
Unison said other universities that had taken Warwick's line had ended up harmonising leave for staff in the same grade after negotiation.