Labour's plans for higher education would cost graduates more than the system being proposed by the Tories, an independent think tank has said.

But the Conservatives' proposals would benefit the rich more than the poor, according to research from the Institute of Fiscal Studies.

Labour's idea of charging students differential "top-up" fees of between £1100 and £3000 per year, repayable after graduation, was outlined in a government white paper earlier in the year.

The Tories responded with an alternative proposal which promised to scrap all tuition fees but also drop the target of 50 cent of school leavers going on to do a degree.

In a Commons debate on higher education funding on Wednesday, Conservative spokesman Damian Green said the government's own research showed that graduates no longer receive the £400,000 lifetime salary boost from a degree that ministers had boasted off.

And he challenged the purpose of the 50 per cent target which he said was putting political ends before academic standards.

"Students and their parents have been let down by the government," Green concluded.

Education secretary Charles Clarke replied the Conservatives had refused to subject their proposals to the scrutiny of the Commons education select committee as he and the Liberal Democrats had done.

He said the IFS research was an example of the "same old Tory" policy of charging the poor more.

"The truth of the Conservative proposals is that they mean less students, less resources for universities and less freedom for universities," Clarke argued.

Reducing the number of graduates would also damage the economy, he said.

IFS researchers have costed the policies from both main parties and found that there would be little difference in the overall cost to the taxpayer.

Public funds would pay universities £1.8 billion a year under Labour and £1.7 billion under a Conservative government, the IFS calculated.

But a breakdown of who would foot the bulk of this bill revealed much sharper differences between the two parties.

More students would benefit from a university education using the white paper plans but graduates, more likely to be higher rate income tax payers, would pay a greater share of the costs.

Using the Conservative idea - branded by the party as "a fair deal for students and parents" - the richest households would pay less at the expense of the poor, fewer of whom would go to university and more of whom would pay for others to do so.

"This pattern of gains and losses would be driven by the fact that under the Conservative proposals, lower-income taxpayers (who are less likely to be graduates) would bear more of the total costs of tuition than under the white paper," the report found.

"In addition, fewer people from lower income families would be likely to go to university."

Under both proposals, students would be better off while studying than under the current system, which has left universities starved of cash for equipment, research and staff salaries.

There would be little difference for students between the parties plans during an undergraduate course, but Labour would ask graduates to pay back loans for longer.

Compared to an average seven year stint of repayments currently, the Conservatives would add one year to this total.

The white paper plans would require 10 years of debt repayment from a graduate moving straight into continuous work.

Green said the two year difference "in itself will act as an incentive to children from lower income backgrounds to apply to university".

"The white paper reforms would ask graduates to pay more of the costs of attending university and would extend the reach of the university system," said IFS research economist Greg Kaplan.

"On the face of it, this seems fairer and more efficient than asking taxpayers in general to pay more for each student, as the Conservatives propose.

"But the success of the white paper proposals depends crucially on whether the government can persuade young people that taking on bigger loans should not deter them from entering higher education, given that the amount they have to pay back each year depends upon their income after graduation."

The National Union of Students said that neither the government nor the Conservatives have "got it right with their plans to fund higher education".

"Neither of them are providing students with the support they need to get through university," president Mandy Telford told ePolitix.com.

"There is little surprise that Conservative proposals are even worse for students from poorer backgrounds - a redistribution of wealth from poor to rich is in line with Tory tradition of only looking out for the wealthy."

Telford added that the Conservative plans to scrap the 50 per cent entry target was "wrong".

"We believe that widening access to education is essential," she said.

"We want to see people from backgrounds who have never been to university before being able to access it.

"At the moment under the current arrangements they can't, under the white paper proposals they still won't be able to, but the Tories just abandoning it entirely we believe is wrong."

Students and universities should be funded through an increase in direct taxation, Telford argued.