A leading government adviser on 14 to 19 education reforms has said he is "beginning to question" the idea of pupils studying all the sciences together at GCSE level.
Sir Mike Tomlinson said the policy, which was designed to create a generally scientifically literate population, may be failing to meet the needs of pupils who want to study science at A-level and university and go on to science-related jobs.
Many schools have reported huge difficulties in recruiting specialist chemistry and physics teachers. Biology teachers, who are in more plentiful supply, are often obliged to teach subjects they have not studied beyond GCSE themselves.
Sir Mike said: "Kids are very sharp. They know when someone doesn't know their physics."
The former chemistry teacher said the policy had created a knowledge gap between GCSE and A-level that could prove demoralising and put off future generations of scientists.
Addressing the annual conference of the Association for Science Education in Liverpool last week, he said: "I backed the policy when it was introduced in the early 1990s, but I am beginning to question it.
"We need young people and adults who can separate the truth from the fiction in newspapers, but we also need that smaller group who want to be very scientifically competent. There is some debate in my mind whether the single package can achieve these aims."
Sir Mike's comments add fuel to the debate about what children should learn in science lessons and complaints from leading scientists of dumbing down. The Government has already tried to address the problem by introducing a slimmed-down core curriculum, leading to a single science GCSE, a core general science award.
Most pupils also opt for a second exam in science, taking options ranging from a generic academic course to individual separate sciences or applied sciences. But the Government hopes that schools will offer pupils who score highly in their Sats a chance to study three separate sciences at GCSE.
Sir Mike said part of the problem could be solved by improving teachers' access to subject-specific training by giving them vouchers to spend on courses as they saw fit. A Wellcome Trust report found last year that half of science teachers had not had any such training during the past five years.
Sir Mike told The TES: "Teachers need to have the capacity to make their own decisions and find training that suits their specific professional needs. Some schools are already doing this."
He said that he thought the Government should consider adding an extra day's training to teachers' contracts to cover such training.