Schools and colleges are furious about the proliferation of new assessments, which cost up to pound;95 each. They warn that preparing for the new exams is eating into teaching time and adding to student anxieties, while those from poorer backgrounds may simply not bother applying because of the cost.

Sixth-formers applying for medicine could end up paying pound;181 to enter three separate admissions tests, while companies are charging up to pound;495 for test coaching. Swansea is one of the universities that is using tests for medical students.

Many of the new exams - launched because universities feel they can no longer rely on A-levels to select students - must be taken in schools and therefore add to administrative headaches, heads warn. Gareth Pierce, chief executive of Welsh exam board the WJEC, acknowledged there had been a “failure to give higher education valid information about students”.

He told a conference of sixth-form heads in Cardiff that this was why work on revising specifications for A and AS-levels from 2008 was crucial.

He added: “Universities are saying that these tests are open to all, but there are fees to sit some and coaching is not available to everyone. Are they therefore being delivered in a fair way?”

In the past three years, at least 11 new tests have been unveiled, mainly by leading universities selecting for the most prestigious subjects. They have to choose from students of whom almost all have at least three A grades.

There are three tests covering medicine alone, with students having to choose the one set by their chosen university.

Eleven universities, including Oxford and Cambridge, have a test for law.

Oxford now sets its own history exam, while Cambridge has tests for modern and medieval languages, maths, and for computer science, natural science, engineering and economics.

Oxford is also introducing tests for physics and maths this year.

Meanwhile, uniTEST, a “generic” admissions test, is being trialled by four universities this year.

All of them emphasise thinking skills. The designers say they do not need much preparation, but teachers warn they will have to find time for coaching.

Sue Kirkham, president of the Association of School and College Leaders, said: “A lot of our members feel that many pupils are not going to bother with these tests.

“It costs money, you have to practise, and you feel those from better backgrounds will do better.”

Natalie Crawford, 17, an AS student at Portsmouth grammar, said: “This is quite scary.”

Universities said they sympathised. But Cambridge said it could no longer rely on A-levels.