It is difficult to know who should be most shocked by the news that university principals enjoyed an average pay increase last year of 4%.

Perhaps it should be the university staff who are currently taking action over a pay offer of 1%. Or maybe it should be the thousands of lecturers who are on zero-hours contracts. Or should it be the taxpayers who provide around half of all university funding?

The answer is that every lecturer, student and taxpayer should be disappointed by the lack of restraint shown on executive pay in Scotland's universities. The news of the big pay rises should also concern everyone who is disturbed by the differential in pay between the bottom and the top in society - a divide which Oxfam highlights in a report published today.

Universities Scotland, which represents principals, uses a number of familiar arguments to defend the rises. Many of the increases, it says, are merely correcting several years of below-inflation rises. It also says universities are huge and complex organisations that need talented, well-paid men and women to run them. And, finally, it says, universities are efficient users of public funding.

There is an element of truth in all these arguments. Some principals have shown restraint in recent years - and some continued to do so last year - and it is true that the principal of a university is a highly demanding and difficult job. Universities also make an important contribution to the Scottish economy by attracting students and academics from all over the world and supporting research and development, and they help boost the UK's status as a leading provider of the best-quality education and training.

However, not even these important contributions can exempt universities from an appropriate show of restraint on pay. Principals have been telling their staff in recent weeks that a 1% rise is the best they can expect in the circumstances, but in many cases the principals themselves have been accepting higher-than-inflation rises to their own pay.

It is hard to avoid using the word hypocrisy in such circumstances - at the very best it displays what the Universities and Colleges Union describe as a lack of self-awareness by the principals. If they are imposing what are effectively pay cuts on their staff, they should accept similar cutbacks themselves on the principle that if pay restraint is required in an institution, it should apply from the bottom right to the top.

In defending the rises, Universities Scotland says more than half of university funding comes from the private sector but by the same argument almost half comes from the public purse, which means these pay deals must be subject to the closest scrutiny. It may be time to look again at the make-up of the remuneration committees which determine pay and consider a role for students and staff.

Scotland's universities are a great credit to the country, but the disparity in pay between those at the top and the bottom is also a cause for concern. Universities cannot fix the problem alone, but they must accept that if the need for restraint on pay still exists, it must apply to everyone.