Three UK universities have lost their place in the top 200 of a global higher education league table.
The universities of Reading, Dundee and Newcastle slipped out of the top 200 of the Times Higher Education (THE) World Rankings for 2014-15.
Five others - Heriot-Watt, Keele, Liverpool John Moores University, Loughborough and the University of Surrey - are no longer in the top 400.
However, Oxford, Cambridge and Imperial College London remain in the top 10.
Holding on to the top spot for the fourth consecutive year is the California Institute of Technology in the United States.
Harvard University is in second place and the University of Oxford is in third.
London has the greatest concentration of first-class universities with four in the top 40 - more than any other city in the world - and seven in the top 200.
Leading Asian institutions are continuing to rise up the rankings.
Asia now has 24 universities in the world top 200, up from 20 last year. Two Asian universities - Tokyo University and the National University of Singapore - now make the world top 25 and six others make the top 50.
The rankings rate universities worldwide on 13 measures including teaching, research and international outlook - such as numbers of overseas students and staff.
Phil Baty, the editor of THE World University Rankings, said that, while the UK had more top-200 universities than any other nation except the US, the new data raised a number of key concerns.
"Overall, the UK's representation among the world's leading universities is declining - three leading names fell out of the top 200 this year, and two others occupy 198th and 199th place.
"Five UK universities lost their top 400 places. This loss of power and influence is not good for the UK's overall competitiveness in the global knowledge economy."
Mr Baty also raised concerns about the dominance of the south-east of England in the rankings.
"The five top UK institutions in the world are all from the South East 'golden triangle' of Oxford, Cambridge and London. Indeed, of the nine English universities in the world top 100, six are from London and the South East."
Reading University Vice-Chancellor, Sir David Bell, said although the placing was disappointing, "we do remain ranked among the world's best universities.
"We do world-class work on issues of critical global importance like climate change, food security and public health. And we have long-term investment plans in place as we seek to return to the top 200 as quickly as possible.
"One cannot read too much into a single year's rankings. Global league tables are highly volatile indicators. The fact that some UK universities have risen and fallen up to almost 40 places year-on-year shows it is much more important to look at longer-term trends over time."
Sir David said pressure from overseas institutions showed "the critical importance for government to sustain research funding and implement a clear immigration policy so we keep the doors open to talented overseas students and staff."
A spokesman for Dundee University said: "This latest result comes in the context of improved standings for Dundee in several other league tables, including the 2014 National Student Survey, in which we achieved record results, and the latest Times Higher Education Student Experience Survey, which rated us top in Scotland and joint 4th in the UK.
"The THE World University Rankings demonstrate the increasing competition facing UK universities from higher education institutions in emerging economies across the world."
A Newcastle University spokesperson said: "It is of course disappointing to drop down to 202 in the Times Higher rankings, but, in the case of THE there does seem to be a sector-wide effect with many more UK universities losing ground to Asia-Pacific institutions.
"This may be as a result of the methodology, or the simple fact that other universities have improved at a faster pace than the UK as a result of increased government investment."
Levels of research income for the university were more than £120m, student satisfaction was high and 94% of Newcastle graduates were in work or further education within six months of leaving Newcastle, the spokesman added.
The general secretary of the University and College Union, Sally Hunt, said: "We have to recognise that our standing is under threat if we don't match our competitors.
"The Asian countries are seeing their universities climb the table because of strong support from government, while we face further cuts. Unless we wake up to this reality, we risk falling behind."