Students in England now pay, on average, the highest university tuition fees in the world, around six times more than those studying in Switzerland and Italy.
And fees could rise even higher after it was announced universities could decide how much they charge if they can prove they offer good-quality teaching.
England topped the list, published by the Organisation for Economic Co-operation and Development (OECD), for the first time - beating even the US.
The report is the first to analyse and compare data after the fee cap in England was inreased to £9,000 in 2012. The US had the second highest average fees at around £5,300 - although Ivy League universities still charge significantly more than institutions in the UK
The government's Higher Education green paper, published earlier this month, also proposed to allow ministers to raise tuition fees.
It outlined plans to allow ministers to set tuition fee caps; currently, any fee rise has to be through secondary legislation and approved by a vote in parliament.
If the plans in the paper go ahead, it could mean some universities would be able to charge significantly higher fees than others.
The proposals, announced by universities minister Jo Johnson, were described as a "direct assault on the rights of students" by the National Campaign Against Fees and Cuts (NCAFC) group.
Responding to the study, Sir Peter Lampl, of the education charity The Sutton Trust, said: "This important international evidence shows that English students pay more for university than their counterparts elsewhere.
"While this has not yet reduced the numbers of poorer young students, it has seen a big fall in numbers of mature part-time students, an important group of access students too often forgotten.
"These figures should cause the Government to avoid steps that could hamper access, including replacing grants for poorer students with loans leaving them more indebted than richer students, cutting widening participation funding, or reducing the independence of the access regulator."
Sorana Vieru, NUS vice president for higher education told HuffPost UK: "Saddling students with enormous amounts of debt is simply unfair.
"Once again, access to education for groups including mature part-time students has been brushed under the carpet. Government cuts to widening participation funding and the planned conversion of maintenance grants to loans risks putting people off applying for university, or dropping out once they are through the door of their institution."