Almost all secondary science teachers say they are limited in giving pupils proper opportunities to do experiments, according to a survey published today.
Practical science work is being hindered by a crowded curriculum, too much assessment and rowdy pupils, the network of Science Learning Centres poll found.
A content-heavy curriculum was identified as the biggest problem, blamed by 69 per cent of teachers for reducing practical work. More than four in 10 said assessment demands were too frequent and 29 per cent said poor student behaviour was a factor.
Just 10 per cent of the 1,339 teachers who took part in the survey blamed health and safety concerns for a lack of practical work.
Professor Sir John Holman, director of the National Science Learning Centre and the Government's adviser on science, technology, engineering and maths, said he was "alarmed" by the findings.
"Learning science without practicals is the equivalent of studying literature without books," he said. "Experimental evidence is the mainstay of science and the UK has a very strong tradition of scientific practical work in schools."
The findings follow other warnings that the Government has failed to get the science curriculum right.
Lord Drayson, science and innovation minister at the Department for Business, Innovation and Skills, conceded at the end of last year that the school curriculum was "flawed".
This came after Professor Adrian Smith, director general of science and innovation at the then Department for Innovation, Universities and Skills, suggested that ministers were educating "the masses" at the expense of equipping the most able with the skills needed by universities and industry.
According to today's survey, the drop-off in practical work worsens as pupils get older. While 63 per cent of key stage 3 teachers said they spent 40 per cent of their teaching time on practical work, that drops to 43 per cent in key stage 4 teachers and just 28 per cent post-16.
Andy Markwick, an advanced skills teacher in Lewisham, south London, said much has changed over the past five years. "The 21st century scheme has very little practical work, there is more focus on ethics and social science," he said.
A spokesperson for the Department for Children, Schools and Families said: "Practical experiments are part and parcel of science classes. The secondary curriculum gives teachers more freedom to teach subjects in engaging and relevant ways, and includes practical experiments."
Original paper headline: Science practicals put on back burner, claim teachers