Scottish universities will be able to charge annual fees of up to £9,000 for students coming to study from other parts of the UK, under new plans.
Mike Russell, the Scottish education secretary, outlined proposals to allow higher education institutions to set their own fees, which would be capped.
The move came after English universities got the go-ahead to charge up to £9,000 for tuition.
Residents of Scotland studying at home will not pay any fees.
Amid concerns over "fee refugees" heading north of the border to study, Mr Russell said Scottish university places for Scottish students must be protected.
NUS Scotland strongly attacked the government's decision, claiming Scotland could become the UK's most expensive place to study for students from England, Wales and Northern Ireland.
And opposition parties in Scotland said the move was an attack on students from the rest of the UK.
In a statement to the Scottish Parliament, the education secretary said he had launched a consultation on legislation allowing universities to set their own fees for students from the rest of the UK from 2012-13.
The move would then be followed by new legislation to cap fees at £9,000 a year from 2013-14 onwards.
Mr Russell said Scottish universities would be free to set fees of between £1,800 and £9,000 for other UK students, but said he expected levels to be lower than those south of the border.
A working group set up by the Scottish government and higher education body Universities Scotland has pointed to an average figure of £6,375.
Mr Russell said: "Scotland has and always will welcome students from all over the world to our universities.
"However, the decisions being taken in England could threaten the quality and competitiveness of our universities.
"We cannot allow Scotland to no longer be the best option and instead be known as the cheap option - we also must protect places for Scottish students."
Mr Russell added: "We are providing clarity for potential students from the rest of the UK that making the positive choice to study in Scotland will not cost more than it does in their home nation."
NUS Scotland president-elect Robin Parker claimed students from the rest of the UK could pay up to £36,000 to study in Scotland, compared to £27,000 in England, because most degrees offered in Scotland take four years to complete.
Accusing the Scottish government of hypocrisy after they rejected a market in tuition fees for Scottish students, he said: "This seems incredibly unfair, especially when the SNP have talked so much about the importance of access to university based on ability not ability to pay.
"We are not at all convinced that increasing fees is required to manage demand. And by introducing a market into education in Scotland, we're seeing some of the worst aspects of the proposals down south come to Scotland, directly against our tradition of fair access to university."
'Lack of clarity'
Usman Ali, NUS Vice President for Higher Education, said the hike in fees "risks erecting a new Hadrian's Wall".
"The lack of clarity as to whether the UK government will provide an additional year's fee loan for English students to study Scotland's four-year undergraduate degrees is deeply troubling and there are many unanswered questions about where the funding is coming from," he said.
"This could either leave English students studying in Scotland faced with finding an additional £9,000 from their own pockets to complete their four-year degrees or a massive hole in treasury budgets as English students take out £36,00 loans from the UK government to study in Scotland."
The SNP has previously given a commitment not to re-introduce fees for residents of Scotland studying in their home country, either on an up-front or graduate basis.
The move is backed by Scottish Labour, the Scottish Liberal Democrats and Scottish Greens, but not the Scottish Conservatives.
Scottish Tory education spokeswoman Liz Smith questioned the legality of the fees plan, adding: "It simply does not send the right message when we are targeting a certain group of students to carry the can for all others.
"If Mike Russell's plan is to stir up resentment in the rest of the UK against Scotland then he might well succeed - this measure is ill-thought out, vindictive and does nothing to address the long-term funding pressures faced by the higher education sector in Scotland."
Labour's Ken Macintosh added: "There is a real danger that the SNP's plans to over-charge students from the rest of the UK will be counterproductive.
"We need to introduce fees for the rest of the UK students to prevent Scotland's institutions being seen as a cheap option, but this goes so far that these students could be put off all together."
Liam McArthur, the Scottish Liberal Democrat education spokesman, said Mr Russell's announcement lacked detail.
"SNP ministers have promised to keep higher education free for Scottish students by raising money from fee-paying English students," he said.
"But today's announcement suggests that four-year degrees at Scottish universities may become more costly than options south of the border. That is a concern."
Mr Russell also announced a review of the way Scotland's colleges are run, led by Prof Russell Griggs, chair of Dumfries and Galloway College's governing body.