Scotland's universities "will suffer" unless they receive an extra £100m to compete with the introduction of top-up fees in England, they have claimed.
The government wants to introduce top-up fees in England
Under the government proposals, universities south of the border will be able to charge students up to £3,000 a year to fund their tuition.
Scottish universities said they needed extra funding to remain competitive.
The Scottish National Party and Scottish Socialists also raised fears of the impact north of the border.
Many universities believe they will find it harder to attract research funding, and thus staff, as a result of the proposals.
They are also worried that Scotland's degrees will be much cheaper than those south of the border, with the result that English students will chose to come north for their degrees - putting more pressure on the Scottish system.
PLANS AT A GLANCE
Existing upfront fees end 2006
Fees then vary - up to £3,000 a year with repayments once graduates earn £15,000+
Students from poorest homes to get up to £3,000 of help a year made up of:
- £1,200 fees subsidy
- £1,500 means-tested grant
- £300 university bursaries
Means-tested £1,000 grants from 2004 rising to £1,500 from 2006
Low-interest student loan up to £4,000 a year
Loan and fee debts written off after 25 years
New access regulator
However, the Scottish Executive said that university funding north of the border was already 20% higher than in England, with 50% of young people in Scotland in higher education.
And ministers have said they are confident that Scottish universities will be able to cope with any knock-on effects arising from the English legislation.
'Close the gap'
A spokesman for the umbrella group Universities Scotland said it would need £100m in funding and warned: "Anything less than that and Scotland will suffer."
He said: "Today should act as a spur to the politicians in Scotland to realise that something has to be done - £100m will not close the gap but, in combination with new ways of working, we think it can keep us competitive."
The National Union of Students (NUS) Scotland said Scottish MPs should vote against the government.
NUS Scotland president Rami Okasha claimed the government was "riding roughshod" over the choices available to Scottish students.
Tommy Sheridan said students in Scotland will lose out
"Any Scottish MP who votes for these proposals will be denying Scottish students places at universities," he said.
Enterprise Minister Jim Wallace conceded that the fees would an impact in Scotland.
But Mr Wallace said Scotland already has "a competitive edge" when it comes to higher education funding.
"The fact that we set up a higher education review (shows that) we could see there was a potential knock-on effect for Scotland," he said.
Scottish National Party MP Annabelle Ewing said the introduction of top-up fees in England "will be a disaster" for Scotland.
Ms Ewing, the SNP's education spokesperson at Westminster, said every Scottish MP should vote against top-up fees as they would harm education in Scotland.
"Labour, Tories and Lib Dems in Scotland are in total disarray over how to respond to English top-up fees," she said.
Scottish Socialist Party leader Tommy Sheridan said students north of the border "are condemned to years of struggle".
He said: "New Labour has destroyed free education despite most ministers having benefited from it.
"This sad situation is now to be made worse in Scotland. Here, students are compelled to repay graduate endowment and loans at only £10,000 a year.
"But fees in England are not to be repaid until income reaches £15,000 a year - while students in England will also benefit from a more generous maintenance grant scheme."