Institutions that have adopted a retake “ban” include the medical school at University College London (UCL) and Bath University’s architecture course, one of the most respected in the country.

Critics argue that the methods used to weed out candidates are becoming so complex and change so frequently that they are unfair on pupils and schools.

Other universities are making increasing use of the A* grade at A-level, which will be awarded for the first time this summer.

Churchill College, Cambridge, which has published admissions requirements for 2011, will require candidates wanting to study law to obtain two A*s, the toughest standard offer in the country.

Many pupils are entered for A-level exams in January of their final year at school, allowing them to retake the paper in the summer if they think they can get a better result.No figures are collected centrally, but government research has suggested that 30%-50% of pupils retake some papers.

UCL’s medical school includes high-profile London teaching hospitals such as University College hospital and the Royal Free.

It argues that the newly published policy is simply making explicit an approach it has long adopted and is trying to “minimise the attrition rate” for a course that includes a large number of exams.

The policy says: “We find that students who need to resit exams to achieve the required grades at AS or A-level tend to struggle subsequently on our programme. For this reason, we will not consider any resit grades at A-level.”

In addition, UCL says almost all exams must be sat in the summer, rather than being staggered “to ensure students can cope with a large exam load”.

Stephen Borthwick, headmaster of Epsom college in Surrey, said he may now advise pupils against applying to study medicine at UCL.

He said several potential candidates were halfway through an A-level course that was structured to include possible resits and January exams and that they could not be expected to reconfigure their course to suit one university.

“To do this across the board is very brutal as many schools choose to take particular combinations of exams to maximise opportunities for their youngsters,” said Borthwick. “To be told this midway through your course is very difficult.”

Universities are having to sort through growing numbers of pupils with straight A grades at A-level. This year, 27% of grades are forecast to be As and about one in eight pupils to score at least three As.

The new A*, introduced to help universities pick the best candidates, are expected to be awarded in about 7% of papers.

To gain an A*, candidates must score an average of 80% for their whole A-level and 90% in exams in the second year of their course.

Only a few universities now use the A* in offers, including Imperial College London and Cambridge, where one A* is the standard offer. Others, including Durham, are considering introducing it next year.

None, however, has gone as far as Churchill College’s law policy. “We are a very data-focused college for admissions,” said Colm Caulfield, one of Churchill’s admissions tutors. “Our law director of studies has an exceptional record for [his students’] academic performance. He believes it is very important to have people with a very high level of academic achievement.”

Caroline Aspinwall, principal admissions officer at UCL medical school, said: “Analysis of the performance of current students revealed that some were struggling academically and with stress, and/or failing medical school examinations, despite having top grades at A-level.

“Some of these students are accustomed to being able to resit exams.”

Katherine Lloyd Clark, head of admissions at Bath, said the policy had been followed for several years, adding: “This approach reflects the exceptionally high demand for our limited number of architecture places.”

Not all schools are opposed to the ban on retakes for university admission. Jackie Cahalin, headmistress of Lancaster Girls’ Grammar school, said: “I can quite understand why they say they will only take you on your first go.

A General Body meeting took place on Wednesday which was attended by around 350 teachers of DU from various science departments such as Physics, Chemistry, Botany, Zoology, Electronics and Computer Science. It was unanimously decided by them to reject the new course.

The Academic Council had met on May 13 and decided that the semester system would be implement in all science courses except B.Sc.(H) Mathematics and B.Sc.(H) Chemical Sciences.

The General Body of Science rejected the semester system as they claimed that Vice Chancellor Deepak Pental had passed the system illegally and without prior consultation from the concerned departments. The science faculty also decided that they would not be teaching any courses that are under the semester system.

Secretary of the General Body of Science, Vinay Kumar Singh, said that all teachers wanted the courses to be taught in the usual annual format and retaining the old syllabus for the course.

Another move by the Academic Council that was protested against by the teachers was the scrapping of the B.Sc. Applied Physical Sciences courses like Computer Sciences and Electronics and merging them with the B.Sc. Physical Science course.

The Delhi University Teachers’ Association (DUTA) was also approached by the General Body of Science, urging them to decide unanimously to oppose the semester system being implemented for undergraduate courses without discussion or debate.

The General Body also asked DUTA to discontinue its involvement with the DU admission procedure that is set to begin this Friday.