However, according to the National Association of Headteachers, the emphasis on raising standards in literacy has been a success.

This year's primary school test results showed a 5% improvement in English, which the government claimed was a result of initiatives such as the 'literacy hour', in which schools dedicate an hour a day to reading and writing.

Schools have made great efforts to achieve the government's targets for literacy

But in a survey of headteachers in England on the impact of the literacy campaign, an overwhelming majority say that it has meant reducing time spent on other subjects.

For five to seven year olds, 70% of headteachers say history has suffered as a result of the extra emphasis on literacy.

Among the seven to eleven year olds, 73% of headteachers say that geography has been adversely affected, with 68% saying history has been reduced.

There has also been a squeeze on the teaching of art, music, design and technology, and physical education, say headteachers.

There has also been an additional financial cost to implementing the literacy strategy, the survey says - with a total cost estimated at £40m for primary schools in England.

The extra money has been spent on additional staff - such as extra assistants to help with reading - and in buying books. A quarter of schools reported spending an extra £5,000 on books.

The survey also shows that there has been an almost total implementation of the literacy hour, even though it is voluntary.