The literacy hour is threatening Britain's international reputation for primary science by cutting the subject to the bone, according to a national school survey.
More than 10 per cent of science lesson time has already been lost because of the pressure on teachers to boost literacy, the survey for the Association for Science Education has found.
Spending on science books and equipment has been slashed since the introduction of the literacy hour, reported one in three teachers in a survey of 525 UK primaries.
England currently ranks near the top in international league tables of achievement in primary science. However the ASE believes the country's standing cannot be maintained without more time and resources.
Rosemary Feasey, the association's chair and lecturer in primary science education at Durham University, said: "While the ASE acknowledges that the introduction of any major new initiative is bound to have an effect on other subjects, it is very concerned with the extent of the negative repercussions on the core subject of science.
"Science has been one of the major curriculum successes in primary schools and this has been confirmed by the findings of the Third International Mathematics and Science Survey.
"England's international status in this area is impressive and anything that might jeopardise our standing should give us cause for concern."
Many teachers had tried to strengthen science by integrating it into literacy work, according to the survey by academics at Durham University's curriculum, evaluation and management centre.
At least half had used a science text during the literacy hour while more than one in three incorporated it in other ways, such as discussing scientific vocabulary or studying diagrams and pictures.
But more training was needed to help teachers maximise the literacy hour's potential benefits for science, said ASE chief executive David Moore.
Meanwhile most teachers had been given less science-based training since the introduction of the literacy strategy. Nearly half had had their science-based in-service training postponed, mostly for two years or more, to make way for literacy training.
More than four out of 10 teachers now spend less time planning science lessons and monitoring progress, the survey found.
Infants spend one hour and 40 minutes a week on science, down from nearly two hours the previous year. Juniors spend just over two hours a week on science, 10 per cent less than in 19978.
More than 80 per cent of teachers surveyed said they were under more pressure since the introduction of the literacy strategy. Three out of five said they were worried about the adverse effect the literacy hour was having on science.
One respondent said: "Literacy takes a disproportionate amount of time. Science is rapidly losing its momentum and its significance in the curriculum."
Another added: "I really feel the clock is ticking. If you don't understand a concept first time - well hard luck, as we're moving on without you."
Curriculum 2000, 21