Medical students from England could be charged up to £15,000 to study in Scotland under plans being considered by the Scottish Executive.
The executive is consulting on charging higher fees
Ministers fear the introduction of top-up fees in England could see an influx of its students to Scotland in search of cheaper courses.
To prevent this, the executive wants to charge similar fees to those being brought in south of the border.
It hopes the move will protect places for Scottish students.
The government believes the plan will also ensure there are enough doctors with a long-term commitment to Scottish hospitals.
Research has shown that about 35% of graduates from Scotland's five medical schools immediately leave Scotland to work, mostly in England, while around half of recruits to Scottish medical faculties are English.
Minister for Lifelong Learning Jim Wallace announced the move to increase tuition fees at Scottish universities for students from England last June.
He suggested the fees increase between £500 and £700, making the total somewhere between £1,700 and £1,900 per year.
Mr Wallace said this would prevent Scottish universities being flooded with students from England when fees there go up to £3,000 in 2006.
The executive is launching a formal public consultation on the plans which it said would be in "broad parity" with English university charges, which are widely expected to reach £15,000 for a five-year course.
The director of Universities Scotland, the umbrella body for the country's higher education sector, David Caldwell, said: "The motive behind this is actually to ensure that opportunities for Scottish students are not damaged.
"If the price in Scotland were to become much lower than in England, there would be a temptation for English students to come north of the border and the problem with is that it would reduce opportunities for Scottish students.
"Let us remember the great majority of Scottish students will continue to pay no fees."
However, he denied that there was any discriminatory element to the move and said English students would still be welcome within Scotland's university system.
"I don't think we are discriminating against English students," added Mr Caldwell.
"They will be paying roughly the same if they study in Scotland as if they remained in England.
"What we're doing is maintaining a level playing field as between the choice they make between Scotland and England."
The National Union of Students (NUS) has always been against charging more for students from England and believes it would set a precedent for top-up fees in Scotland.
The president of NUS Scotland, Melanie Ward, said: "Our concern is that the measure could be extended to Scottish students and therefore it would affect them as well.
"We're worried that the current proposals are the thin end of the wedge. The legislation is very much enabling legislation, it allows the minister to begin with higher fees for medical students in England and then to extend that to other courses without further primary legislation.
"In a couple of year's time that could be extended to Scottish students."
Miss Ward added that much of the talk about the introduction of fees was currently based on speculation.
She called for the executive to take a "more measured" look at the situation before it made any final decisions on the proposals and brought in the fees.