The architect of the government's plans to extend education maintenance allowances to higher education this week called for the scheme to be restricted to the poorest families.
Wendy Piatt, a senior research fellow in post-16 education at the Institute of Public Policy Research, devised the maintenance scheme to support 16 to 19-year-olds from low-income families in full-time education.
But leaked proposals suggest the government is planning to extend the allowances to students in higher education from families with an income of up to £30,000.
Dr Piatt, who believes the threshold should be set at £20,000, said:
"The point is to give money to those who need it."
The original proposal, announced by chancellor Gordon Brown in July's spending review, was for an education maintenance allowance that would give £1,500 a year to young, full-time students from low-income families - although the income threshold was not confirmed.
Prime minister Tony Blair is reported to be concerned that even a threshold of £30,000 would provoke a backlash across middle England. Downing Street is said to be pressing for last-minute changes to the scheme because middle-class parents would bear the brunt of the costs.
David Rendel, Liberal Democrat higher education spokesman, said: "I would have thought this scheme was pretty inadequate for students' needs. Liberal Democrats have long argued for the re-introduction of maintenance grants and for the abolition of tuition fees and, while the government's recognition that grants should be restored is welcome, £30 per week is woefully inadequate."
Tim Boswell, shadow higher education minister, said: "We have to look at who is paying for it. Is it a transfer of money from the middle classes to socially excluded students? The implication is it will be an elaborate shuffling exercise."
A spokeswoman for Universities UK said: "The key is that the review should lead to a targeted system of student support that is simpler to understand and to administer."
Data from the Office of National Statistics show that the average gross annual household income for the lower social classes - skilled, semi-skilled and unskilled manual workers - is £25,600. About 26 per cent of entrants to full-time higher education in England come from these groups.
* Some 41 per cent of students would vote Liberal Democrat if there were a general election tomorrow, according a website that campaigns against student debt.
In the poll, PayUpTony.com asked 2,700 voters which way they would vote. Some 40.8 per cent said Liberal Democrat, 21.0 per cent other, 20.2 per cent Labour and 18.1 per cent Conservative.
The Liberal Democrats were instrumental in seeing the Cubie proposals implemented in Scotland. Scottish students no longer pay up-front tuition fees and there are bursaries for the poorest students. This year, Scottish university applications were up 4.4 per cent while the number of school-leavers applying to English institutions fell.
Some 75,000 students have now signed the website's petition.