The Lib Dems say the average graduate debt will be £15,000
The average female graduate will take 21 years to pay off her debts if the government's plans to increase tuition fees are approved, the Liberal democrats have warned.
Women who want to buy their own homes will effectively face servicing "two mortgages", a spokesman added.
The figures are based on an average female graduate, who will have two children and earn less during her working life than most men.
The government is planning to introduce variable tuition fees of up to £3,000 a year from 2006. The current fixed figure for all courses is £1,100.
'Terrible waste of talent'
Lib Dem work and pensions spokesman Steve Webb said: "Top-up fees will create huge debts which will have a particularly bad
effect on young women thinking about whether or not to stay on to
"On average, women graduates will earn less than men, and
they are more likely to have a career break to start a family, so their
debts will take longer to pay off.
"Faced with the prospect of decades of debt, many young women will simply decide that university is not for them. This would be a terrible waste of talent and shows why the top-up fee policy is so misguided.
"I do not see how people are expected to buy a house, start saving for a pension and pay back two decades worth of student debt all at the same time.
"The sums just don't add up and for many it will be the university
course that goes".
The Lib Dems' figures are based on an average student debt on graduation of £15,000.
They assume salaries increases in line with average earnings growth, which is estimated to be 4.5% a year.
The government says the proposed tuition fees increase is needed to fund its plans to get "towards 50%" of young people into higher education by 2010.
It is reintroducing student maintenance grants of up to £1,000 a year to offset some of the cost.
A Department for Education and Skills spokesman said: "One of the progressive benefits of our plans is that parents will be able to take time off work and will not have to repay anything during that time.
"Yes, this will mean that it will take longer to pay off the loan but unlike a credit card debt, high rates of interest will not build up and place a heavy burden on the lender.
"Student loan repayments are linked to your income and ability to repay.
"The less you earn the less you repay. This is a fair proposal and means that, unlike debtors that get themselves into terrible credit card debt, the repayments are manageable and represent a small proportion of what you earn."