Graduates could be forced to pay back double their original student loans under the new fees system in England, figures have suggested.
Those who take advantage of a £39,000 loan for a three-year course could find themselves repaying up to £83,000 in cash terms, data collected by leading accountants for the BBC showed.
And parents who seek to pay off their children's debts could face penalties, the Government has said.
But it insists the new system is fair and will lessen the burden on graduates, who are currently obliged to start repayments when they are earning more than £15,000.
While it will remain possible to pay off a loan straightaway, in future such action could incur a cost, universities minister David Willetts told the BBC.
This would mean parents who step in to help their children clear their debts could find themselves penalised.
"What we are looking at is whether, if people wish to repay early having taken out a loan, there should be any payment for that and on that we are going to be consulting people to seek their views," Mr Willetts said.
"The question on which we will consult is whether or not there should be a penalty for people."
Defending the new system, due to come in next year, he added: "For many people, what will matter the most will be the size of the monthly repayments and those, of course, are lower under our proposals than the current schemes because you start paying back when your earnings are more than £21,000 and you only pay 9% of anything above £21,000.
"At the moment you start paying back when you're earning over £15,000, so people's monthly repayments will be lower under our scheme.
"I fully accept that, in turn, means that you'll be quite possibly making those monthly repayments for longer."
Under the new system, graduates could find themselves saddled with a 9% rate for up to 30 years.
The figures, released by BBC Breakfast, were compiled by accountancy firms over the lifetimes of three fictional students.
The calculations were based on the assumption that each student borrowed a total of £39,000 - an annual £9,000 in fees and £4,000 for maintenance during a three-year course.
The notional graduates went on to earn above the national average.