Les Ebdon, head of the Office for Fair Access, said the National Scholarship Programme - worth £50 million this year and £150 million by 2014-15 - was confusing for many students and had not had the desired effect on applications from those from poorer backgrounds.
"There is a recognition that it has not been as effective as it might have been," Professor Ebdon, former vice-chancellor of the University of Bedfordshire, told GuildHE's annual conference at Leeds College of Art on 13 November.
Professor Ebdon said the scheme, which offers students at least £3,000 a year in financial support - including bursaries, fee waivers and on-campus benefits such as rent subsidies - was difficult to market to students as it is not certain who will receive support.
"The biggest issue is there is not a clear line of sight," said Professor Ebdon.
"You are not guaranteed it when you apply and you do not know if you will get it or not," he added.
"There is a big difference in saying you may get something and saying you will definitely get this support."
Students were also sceptical about the programme because a large chunk of support was given as a fee waiver rather than as a cash grant, he added.
"When you pick it apart, it does not end up in your pocket," he said. "Why not just add the money to student grants... it would make it more national."
Professor Ebdon is the latest high-profile critic of the NSP, which is being reviewed by the Higher Education Funding Council for England.
Last week the Institute for Fiscal Studies said it was a "potential deadweight" as it did not attract more university applications from poorer students, while the government's social mobility tsar Alan Milburn called for a "holistic review" of the scheme in a review of widening participation funding.
Mr Milburn called for the government to drop the fee waiver element of the NSP, branding waivers "a total waste of time".
More research was needed to find out what type of spending helped to increase university applications from socially deprived areas, Professor Ebdon also told delegates at the GuildHE conference.
"We spend a lot of time saying how important research is, but when it comes to how we spend our money [on access] there is a lack of research," he said.
With £809 million due to be spent on access in 2015-16, the lack of evidence on effective use of money was a "dangerous thing", he warned.
Comparing spending on access to Aimhigher, which undertook school outreach programmes for universities until it was scrapped in 2011, he said: "When the cuts came calling, [Aimhigher] was not able to demonstrate quickly and effectively its results.
"If we are administering £809 million a year, we need to be doing that."