Labour has a matter of days to show it is "up for the fight" on student finance after electing a leader who backed a graduate tax during his successful leadership campaign, the Labour Party conference in Manchester has heard.
Supporters of such a tax said they were "delighted" with Ed Miliband's stance, but warned that he must quickly get to grips with the complexities of the debate.
However, concerns have been raised within the party - which introduced the current system while in power - that Mr Miliband has boxed Labour into a corner on higher education policy by backing the idea. There are also fears that he does not fully understand the practical difficulties of a graduate tax.
Mr Miliband became Labour leader on 25 September, narrowly beating his brother David who had favoured waiting for the outcome of Lord Browne of Madingley's review of fees and funding next month before taking a stance on the issue.
The result leaves the younger sibling two weeks to get a firm grasp of the debate before Lord Browne's report, which is likely to be published on 12 October.
Les Ebdon, chair of the Million+ group of new universities, which has commissioned detailed research on how a graduate tax might work, said Labour had little time to prepare.
"If Labour wants to change its policy, it will have to be up for the fight - not by the time of the next election, but by the end of next month," he warned a fringe meeting during the conference.
He insisted that a graduate tax was a "fairer, progressive and feasible" option and said statements claiming it would lead to a brain drain were "arrant nonsense".
However, others in the sector questioned Mr Miliband's motives for taking a rigid line before the publication of Lord Browne's report.
Paul Marshall, executive director of the 1994 Group of smaller research-intensive universities, said some might ask whether the move was "a genuine attempt to put forward a proposal or a cynical attempt to oppose the coalition".
He claimed that nobody had been able to resolve practical problems with a graduate tax, such as how to charge European Union students or maintain the link between what students pay and university income.
One Labour source said Mr Miliband had yet to get to grips with the detailed arguments against the tax, and called the decision to back the system before Lord Browne reports a "mistake".
There are fears among some party members that backing a graduate tax now will leave Labour open to counterattacks from the coalition government, which has ruled out a pure version of the scheme.
However, David Lammy, shadow minister for higher education, said he was in "no doubt" that Mr Miliband and his team understood the crucial debate on higher education that was about to unfold.
"We will be seeking to put this administration (the coalition government) under maximum pressure in the decisions that it is taking," he told a fringe event.