The author of a report on international higher education has questioned whether UK universities can remain world leaders without more funding.
The report for Universitas 21 rated the UK 10th best at providing higher education in a ranking of 48 countries.
The study put the UK second for university research and teaching but 27th for spending on higher education.
Universities UK said other more established global rankings regularly put the UK system second to top.
Ross Williams, lead author of the Universitas 21 study, said the evidence showed the UK system was very efficient.
Professor Ross, of University of Melbourne, told BBC News: "The model is that if you want to maintain high output you must maintain high resource levels.
"Think of all the extra resources that are going to higher education in East Asian countries. You are going to have to put in more resources even to maintain your rankings."
Universitas 21, an international group of universities, claimed the new ranking was the first to compare the effectiveness of national higher education systems.
'US tops ranks'
Their analysis put the United States top, followed by Sweden, Canada, Finland and Denmark.
The UK was ranked 10th overall despite coming second only to the United States on the strength of the universities themselves.
It came 27th for the resourcing of universities and 41st out of 48 for government spending on higher education.
The report claims: "The difference in ranking between output and resources is the greatest for all 48 countries and reflects very high productivity."
Universities UK, which represents all UK universities, said it was difficult to compare international education systems - but other more established compilers of world rankings such as Times Higher, QS and Shanghai Jiaotong consistently rated the UK as second behind the United States.
Chief executive Nicola Dandridge said: "League tables cannot tell the whole story... and positions will vary from one table to the next, depending on the selection of criteria and methodology used.
"Based on measures of output and efficiency, the UK remains the second strongest university system in the world after the US.
"It attracts more overseas students per capita than the majority of major higher education systems, and it remains one of the world's leading research powers measured by total publications and citations.
"However, we continue to spend less as a percentage of GDP than the average of OECD countries.
"We should remain acutely aware that other countries are investing more than the UK and that our reputation as a world-class provider of higher education is not a foregone conclusion."