University top-up fees could provide a "disincentive" to studying science, the UK's Royal Society has warned.
Some universities 'may be put off providing science courses'
The costs of laboratory work and field trips might also put institutions off offering courses, education chairman Sir Alistair MacFarlane said.
The government is planning to allow universities to charge students up to £3,000 a year for some courses.
Sir Alistair said this increased the need for "government support" for science from school level upwards.
'Quality of life'
The number of A-level physics students fell by 29.6% between 1991 and this year.
For maths the figure was 25.4% and chemistry 18.7%.
Sir Alistair said: "The plummeting popularity of science, engineering and technology among pupils and students threatens the prosperity and quality of life of the whole nation and its progress during the 21st Century."
He added that the government should allow "no let-up in the efforts to remove the hurdles that are deterring talented young people from studying science. "
Changes to higher education could "accelerate, rather than reverse, the downward trends in the popularity of science courses".
Tuition fees in England are currently set at £1,125 a year for all full-time undergraduates.
Under government plans, universities could charge between nothing and £3,000 from 2006, depending on the popularity and quality of a course.
Sir Alistair said: "Many undergraduate courses in science, engineering and technology are more expensive to run than those in other subjects because they require laboratories, equipment or fieldwork.
"If this differential cost is reflected in top-up fees, this may well introduce a significant disincentive against studying science, engineering and technology at university.
"It could also create an incentive for institutions not to provide the more expensive courses."
Shortages in the supply of school science teachers were also a problem.
Sir Alistair, the former vice-chancellor of Heriot-Watt University, said: "Future generations of UK schoolchildren need
to be encouraged to realise their full potential in science, engineering and technology.
"Science offers a uniquely exciting and creative learning experience that enriches our lives. In addition, we need a plentiful supply of talented individuals to fill the many jobs, especially teaching, that require scientific skills and knowledge.
"We also need a citizenry sufficiently informed and comfortable with the principles of scientific endeavour to help them engage with the many social, cultural and ethical issues that arise from our advances in knowledge."
The Royal Society, which is the UK's academy of science, founded in 1660, works to encourage the development of scientific research and knowledge.