A ban on dictionaries in GCSE and A level exams will be imposed by the Qualifications and Curriculum Authority, as research has shown that pupils were becoming over-dependent on them.

The research, carried out by the University of Birmingham, showed that pupils were using a quarter of their exam time looking up words in dictionaries - an average of once every two minutes.

Dictionaries have helped the most able, but hindered the least able

There was also evidence that the use of dictionaries exaggerated the differences between the exam performances of the better and weaker pupils, as the more able students made much better use of dictionaries.

Introducing the ban, which will apply in England, Wales and Northern Ireland, a spokesperson for the curriculum authority said: "Inappropriate use can hinder the development of important foreign language skills and, in some circumstances, actually disadvantage candidates in examinations."

Nonsensical

Among the "disadvantages" found by researchers were examples where less able students had used dictionaries to translate pieces word by word into French, which wasted much exam time and ended up with "nonsensical" answers.

There were also concerns that the use of dictionaries would deter some pupils from learning vocabulary for themselves, with an over-reliance on dictionaries becoming an obstacle to developing language skills.

The withdrawal of dictionaries from modern languages exams will apply to courses starting in 2001.