The National Union of Students (NUS) said access to university should be based on academic ability and potential, rather than the ability to pay.
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NUS is appalled that, months after the prime minister himself highlighted the issue of student funding, no improvements have been made
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Owain James
The union said the government was failing in its own agenda to widen participation, with thousands of people put off going into higher education because of fears of going into debt.
Graduates were now leaving university with average debts of £12,000, the NUS said.
The union praised the administrations in Scotland and Wales for taking "positive steps" to remove some of the financial barriers - and urged Westminster to follow suit.
Last week the Welsh Assembly announced that student grants were to be re-introduced, with £41m being ringfenced for poorer families.
And in Scotland, the controversial tuition fees have been scrapped and replaced by a system of paying back fees and loans once students have graduated and are working.
'Appalled'
NUS President Owain James said students were going to Downing Street to make their views known.
"NUS is appalled that, months after the prime minister himself highlighted the issue of student funding, no improvements have been made," said Mr James.
"In fact some of the proposals, such as commercial rate loans, will actually leave thousands of students even worse off."
The gesture of discontent came a day before students planned to take to the streets of central London in a protest march.