Academics face a lottery when it comes to discretionary pay. The proportion of lecturers awarded extra income in addition to standard salaries varies dramatically from one old university to the next.
The first detailed breakdown of discretionary pay in pre-92 universities also exposes a stark gender gap. Male academics are up to five times more likely to be awarded optional extra pay than their female colleagues.
Discretionary payments can amount to thousands of pounds a year for senior lecturers.
Research by the Association of University Teachers reveals huge discrepancies in policies between universities. For example, while less than 10 per cent of academics are awarded extra pay at the University of Wales, Aberystwyth, more than a third receive payments at Strathclyde University, the University of Manchester Institute of Science and Technology (now Manchester University after a 2004 merger) and the London School of Economics.
The figures reveal differences across the UK. In English institutions, 20 per cent of lecturers entitled to discretionary pay received it in 2002-03 compared with 16 per cent in Welsh universities.
Stephen Court, senior researcher for the AUT who carried out the study, said: "The likelihood of an academic being awarded discretionary pay is something of a lottery at the moment, depending as much, if not more, on their choice of institution as on the consistency of pay and employment practice in higher education as a whole."
The AUT is particularly alarmed by the gender divide revealed in the figures. Overall, men are one and a half times more likely to receive the award, but there are wide variations across institutions.
At Aberystwyth, 10 per cent of eligible male academics received an award in 2002-03 compared with 2 per cent of eligible women. Among the 50 institutions in the study, only Bradford University rewarded more women than men - per cent against 22 per cent.
Sally Hunt, general secretary of the AUT, said: "These findings are a matter of concern, given the continuing evidence for a gender pay gap in men's favour in higher education."
The figures are based on returns to the Higher Education Statistics Agency and form part of the AUT's submission to the Government's Women and Work Commission, set up last year by Tony Blair to examine the gender pay gap in the workplace.
The AUT is doubly concerned as the new pay framework, to be introduced across the sector over the next 18 months, will make all staff eligible for performance-related contribution points.
Ms Hunt said: "The AUT is firmly opposed to discretionary pay points being used as a form of performance pay because this will make a bad situation even worse for women, who are already less likely than their male counterparts to receive discretionary pay."
A spokesperson for the Universities and Colleges Employers' Association said: "In explicitly promoting equal pay for work of equal value, the framework agreement and subsequent Joint Negotiating Committee for Higher Education Staff guidance on contribution-related progression - both of which were designed and agreed with the unions - include specific commitments and advice on this issue."