Plans to eliminate practical experiments and lab work from A-level science are being opposed by a high-powered alliance of scientists, universities and employers, who warn that the standing of British science could be severely damaged.

The Wellcome Trust and the Royal Society are among critics of the proposals by the Office of Qualifications and Examinations Regulation (Ofqual), for which a consultation period ended.

Score – a partnership of science organisations that includes the Royal Society and the Institute of Physics – is urging the Department for Education and Ofqual to rethink the plan, warning that it "will leave students even more poorly equipped for progression to higher education and employment".

Professor Julia Buckingham, vice-chancellor of Brunel University and the chair of Score, said: "Practical work is an integral part of science, it's not an add-on. It's something that encourages students to question, to explore – it excites them."

Taking practical work out of A-level grades could see schools put less effort into teaching those skills, leaving undergraduates ill equipped to study science at university, Buckingham added. "That will downgrade our science base and make our young people less competitive in the global economy we now live in."

The Wellcome Trust, a global foundation based in London that supports biomedical research, said it was "deeply concerned" by the proposals. Hilary Leevers, head of education and learning at the Wellcome Trust, said dropping practical assessments would damage British science. "I absolutely think that if students are not having practical experiences in schools it would harm their progression, both into university and further study and into employment based on those practical skills," she said.

"You need to be taught those things at school. If you are going on to study biology and you think it's about sitting in a classroom doing written work, then you're going to get the shock of your life when you go into labs in the workplace or in universities."

Last year Ofqual announced its plans to reform A-levels as part of an overhaul ordered by the education secretary, Michael Gove. Under Ofqual's proposals, assessment of a pupil's practical work in biology, chemistry and physics would no longer count towards A-level grades.

The Confederation of British Industry said in its submission that removing practical skills from A-level grades was "a significant step backwards and could undermine employer confidence in the qualification. It would be wrong for a student to receive a top grade in a science subject without displaying strong, relevant practical skills".

In its discussion document making the proposals last year, Ofqual said that internal assessment of practical work showed significant weaknesses, with teachers often awarding similar marks to pupils who received varying grades in A-level examinations. Ofqual also argued that many schools struggled to teach a wide range of skills, while the proposed A-level regime would still examine practical work carried out by pupils.

But opponents said the proposal was further undermined by Ofqual's decision to retain practical assessment in the awarding of science GCSE grades.

"If there are real concerns about the ways in which practical work is being assessed at the moment, then we need to think about new ways of assessing it, we need to pilot those studies before we implement something new," Prof Buckingham said.

"What we all want is for practical work to be assessed, to be assessed properly and fairly, and that the students who receive that assessment have a really good understanding of what they can do."