Writing in Holyrood magazine, Mike Watson MSP said graduates from the past 25 years should pay more to help out modern academic institutions.

The Labour peer said their money would help universities compete with their English counterparts once top-up fees are introduced in the south.

He said the move may prove impractical but was worth consideration.

Mr Watson said: "Why shouldn't all those who have graduated in the past 25 years make a contribution?

"If graduates benefit by earning more than those without a degree, then so do those who graduated over the period when the rapid expansion of higher education took place."

But Tory enterprise spokesman Murdo Fraser described Mr Watson's suggestion as "ridiculous".

Endowment policy

The former tourism, culture and sport minister also suggested the �2,000 endowment which graduates currently pay should be increased.

The endowment, paid by graduates after they leave university, is used to pay for grants and bursaries for students from poorer backgrounds.

But he said increasing the endowment would free up more Scottish Executive cash to plough into universities.

Mr Watson added: "There is no reason the amount they (students) pay should not also increase."

Top-up fees will allow English universities to charge students up to �3,000 per year - a move ruled out north of the border by the executive.

Scottish universities are worried English institutions will become richer and attract more students and staff as a result of the increased funding from fees.