The drive to reward universities that produce the most employable graduates could channel money to elite institutions that rely on their historical reputations with employers.
Lee Harvey, director of the centre for research into quality at the University of Central England, will warn civil servants this month that their forthcoming "employability" performance indicator must be a sophisticated formula and not a crude measure of graduate employment rates.
"We already know that some subjects and some institutions have better employment rates, irrespective of what they do, simply because of their reputation," said Professor Harvey.
He said employability had moved to the top of the higher education agenda and there was increasing pressure for universities to make graduates work-ready.
"The government has pledged to link funding to employability through a new performance indicator. We need to define what this means, otherwise any indicator will be meaningless and, worse, it will be a major setback to the huge efforts already made towards improving employability."
Professor Harvey said it was crucial to decide what matters: the ability of institutions to get graduates into employment; the extent to which graduates are work-ready; or the extent to which employability skills are embedded in the curriculum.
If the aim is to increase the employment rate of graduates, then what jobs should be included within what time frame and for what type of graduates? Should starting salaries and discipline differences be taken into account? And how is a graduate job to be defined? It might be possible, said Professor Harvey, to give different weightings to employment rates in different disciplines, as in the research assessment exercise.
He said: "We need to decide whether a year on work experience counts for more than a semester on a live employer project. Should the teaching of teamwork skills count for the same as time management, risk-taking and leadership skills? There are a lot of questions still to be answered."
Diana Green, vice-chancellor of Sheffield Hallam University, said there was a danger of slipping into manpower planning by the overuse of employability as a criterion for funding. "The challenge for universities will be to balance the pressure to perform well against any employability measures by staying with what we already do well ... against the pressure to encourage enterprise in our graduates."
Peter Knight, of Lancaster University's department of educational research, said: "This outcomes-led approach will collapse under its own weight unless we start to think more about the whole student experience."