Record numbers of students have been caught making false applications to universities, UK authorities say.
The number of cancelled applications has more than doubled
The Universities and Colleges Admissions Service said it had detected 1,000 fake qualifications in 2004 - more than twice the usual number.
The cancelled applications included two groups of 200 submitted by people from China and Pakistan.
In most years the majority of fraudulent claims come from the UK.
Ucas investigates suspicions referred to it by universities.
It also scans all 480,000 or so applications it receives each year for signs of fraud, such as many people giving the same home address.
Foreign students - and those from the UK applying several years after sitting their A-levels or Highers - do not have to produce their exam certificates until they arrive at university.
Checks vary, with grades not always being verified with exam boards.
UK students who apply before A-levels or Highers have their grades passed on to Ucas automatically.
Ucas said the normal number of cancellations in a year was about 400.
A spokeswoman said: "Ucas does not make any admission decisions; this is purely the responsibility of the relevant university or college.
"However, in some cases, a university or college may inform Ucas of concerns and we will investigate the applications further. If there is clear evidence of fraud the applications will be cancelled."
She added that it was important to "ensure that each case is dealt with in the appropriate manner".
Barry Sheerman, chairman of the Commons education select committee, has called for an investigation.
This was backed up by the Conservative Party and the British Council, which promotes the country's interests abroad.
Meanwhile, Oxford Brookes University has expelled 11 students after an investigation into fake qualifications.
The vice-chancellor, Professor Graham Upton, said: "This is a normal part of our admissions process which means that unless proof of qualification is forthcoming, students are excluded."
He added: "We maintain rigour at all times in our admissions process for all students, including those applying from overseas.
"In the case of international students this process is particularly rigorous because they are also required to comply with visa regulations, which includes evidence that they have a university place and the funds to complete their course, including any living expenses."
Birmingham University has also expelled a number of students after an investigation revealed it had been targeted by fraudsters.
The Times Higher Education Supplement reported that an agent for Chinese students had claimed he had fixed university places for hundreds of unqualified students over the past three years.
He allegedly charged fees of several thousand pounds for each case, it added.