Dictionaries are to be banned from foreign language exams following the discovery that they give able pupils an unfair advantage.

Weaker GCSE candidates used dictionaries to try to translate the exam instructions, while more gifted pupils were able to boost their scores substantially, according to new research by Birmingham University.

The ban applies to new GCSE and A-level exams due to be introduced in 2000-1. Currently most GCSE syllabuses allow the use of dictionaries though the picture is more mixed at A-level.

Pupils who used dictionaries boosted their GCSE French scores by an average of 9 per cent, said the researchers, who were commissioned by the Government’s curriculum quango.

However, most teenagers wasted too much time consulting dictionaries. On average GCSE pupils looked up a word at least every two minutes, using up a quarter of their exam time.

The type of dictionary used is crucial. Modern dictionaries which list phrases, and give information on verb forms and letter writing boosted the brightest candidates’ marks much more than old-style formats.

Chris Maynard, languages officer with the Qualifications and Curriculum Authority, said: “This research gave us clear evidence that the availability of dictionaries was widening the gap in achievement between the most able and the weakest students.

“The brightest pupils were able to do even better using a dictionary whereas the weakest candidates mainly used them to check that they understood the instructions rather than using them to improve the quality of their answers.”

Pupils will not be allowed to take dictionaries into the modular AS and A-level foreign language exams to be introduced from September 2000. The same restrictions will apply to modern language GCSEs when the syllabuses are revised for 2001. Candidates will still be able to use dictionaries to complete coursework.

GCSE exam instructions are also likely to be written in English after the study showed that weaker students spent most of their dictionary time trying to translate them.

Mr Maynard said: “Pupils should be taught and encouraged to use a dictionary or glossary to improve the accuracy of their work. At the same time it is essential that they do not become over-reliant on a dictionary.”

Using a dictionary can actually be a disadvantage, according to researcher John Hurman of Birmingham University’s school of education. He said: “Literal transposition of words from English into French was very common, resulting in more meaningless language than could have been expected without dictionary use.”

The researchers examined the effect of using a dictionary in GCSE French writing exams at foundation and higher tiers and the comparative effects of using different types of dictionary in 26 schools.

Dr Brigitte Boyce, director of the Association for Language Learning, criticised the lack of consultation about the ban. “The ordinary classroom teacher is often the last to know about these policy changes.”