Student leaders hit out after new figures showed the number of extra pupils institutions will recruit under a new widening access initiative.
Under the scheme, run by the Scottish Funding Council (SFC), 727 extra funded places were made available to widen access.
In addition, more than 1000 university places have been earmarked for college students under a policy known as articulation.
The figures show St Andrews University, in Fife, will take just 20 students under the schemes while Edinburgh University will take 50 extra students.
In contrast, Glasgow University has been allocated more than 200 additional places, with Dundee taking 200 and Stirling 180.
Robin Parker, president of NUS Scotland, said: "Scotland needs to do more to promote fairer access to higher education. While some universities have taken this message on board, others have shown a disappointing lack of ambition in the number of places they've asked for.
"Those universities that have taken up large numbers of these new places, like Glasgow and Stirling, deserve great credit.
"However, it's incredibly frustrating that others are still dragging their feet.
"St Andrews and Edinburgh continue to demonstrate a severe lack of ambition for fair access and for their own institutions, particularly as they have the most to do."
However, a spokesman for St Andrews said: "We are one of the nation's smallest universities and account for less than 2% of Scotland's university capacity.
"Given that it is now established that so few school pupils from the most deprived areas in Scotland are being supported to achieve basic university entry grades our target is, by any standards, ambitious and fair."
A spokesman for Edinburgh University said: "Widening participation is a strategic priority for the university and we have adapted our admissions selection policies.
"We are committed to playing our part in tackling the under-representation of students in higher education from the most deprived neighbourhoods.
"We recognise these neighbourhoods are predominantly in the west of Scotland, and students from these areas are the least geographically mobile.
"For this reason, we have launched a new accommodation bursary scheme to make studying at Edinburgh a realistic choice for students from across Scotland."
Alastair Sim, director of Universities Scotland, said every university was committed to widening access.
He said: "We have been consistent in saying an incentive approach is more effective and the creation of extra, ring-fenced places follows that model.
"Universities will now get to work on filling these places with bright candidates that have the potential to benefit from a higher education."
Professor Anton Muscatelli, principal of Glasgow University, said the extra funding would allow staff to expand the number and spread of neighbourhoods targeted "to reach more pupils and engage with them from an earlier age".
He said: "We believe universities have a responsibility to make higher education accessible to people from the widest possible socio-economic spectrum."
The row came as the SFC published details of the funding individual universities will get as part of a £1.07 billion settlement for 2013/14. SFC chairman John McClelland said: "This announcement allows universities to continue to enhance their research and teaching as well as support Scotland's economy through knowledge exchange."