The Conservatives are offering a year's free university tuition fees in a text message competition to highlight their policy of abolishing fees altogether.
The Tories say fees deter poor students
Students can text "no fees 4 [institution name]" to go into a draw.
The government plans to vary fees in England from the current flat rate of £1,125 to between zero and £3,000 a year from 2006, payable on graduation.
Tory policy has been criticised because it would prevent large numbers of youngsters from going to university.
'Debt hardly an incentive'
The shadow education secretary, Damian Green, said: "This government has betrayed parents and students across the country. It promised in 1997 not to introduce tuition fees and then it did.
"It promised in 2001 not to allow top-up fees and now it will. Students have a right to be angry.
"If ministers want to encourage students from all backgrounds to go to university then threatening them with potentially £17,000 worth of debt after three years of studying is hardly an incentive."
Analysis by the Higher Education Policy Institute suggests that under the Conservatives' policy there would be a funding gap equivalent to more 450,000 student places.
"A very large number of potential students with at least two A-levels would be unable to gain access to higher education of any sort," it says.
But the Conservatives say the government's target of having 50% of young people experiencing higher education is unnecessary.
Speaking on the Today programme on BBC Radio 4, Damian Green said: "Already you can see there are students being attracted into degree courses that simply do not get any benefit from them, which is why some universities have got drop-out rates of over 40% which clearly does the students no good at all."
But the head of the government's university admissions taskforce, Brunel University vice-chancellor, Steven Schwartz, said many other countries had passed that 50% target.
"It may seem utopian to Mr Green, but it is being done all around the place. Many people have ambitions for their children.
"To dismiss the legitimate ambitions of working class families in that sort of cavalier manner to me is a very negative view of the future."
And he said fees in other countries had not deterred poorer students.
"We have had a deferred payments system in Australia for many, many years. The number of people from low income families has actually increased."
Prof Schwartz added: "Every time there is any conflict between excellence in higher education and saving money, saving money always wins, because the government is paying the bill and it has higher priorities, it has health, it has schools it has law and order.
"We are not a high enough priority to actually get a hold of that money. Go around universities, have a look at them. They are falling down, they are falling apart.
"Where is the extra money going to come from to provide the level of excellence we wish to provide? Certainly it is not going to come from a party that does not want to have any fees."
The leader of the country's vice-chancellors, Diana Warwick of Universities UK, has said universities are "desperate" for more funding.
She said graduates needed to contribute more to the system, as the government plans, or there would be a "deterioration" in standards.
The Tory competition is open to all UK students - even though those in Scotland have their fees paid for them. In England and Wales, about 43% pay no fees and 16% make a partial contribution.