Foreign science students could be deterred from studying in the UK by new checks aimed at stopping the spread of weapons technology, it is feared.
Foreign students are a good source of university revenue
The Academic Technology Approval Scheme will require non-EU postgraduates who want to study "proliferation-risk" science subjects to apply for approval.
Currently the Foreign Office is alerted by universities voluntarily about applicants from "countries of concern".
It says it is not in anybody's interest to penalise bona fide students.
The registrar of the Royal Society of Chemists, Tony Ashmore, told his organisation's own publication Chemistry World that there was a security issue that needed to be addressed.
But he said the UK must remain "open to students and academics from around the world" and that they were extremely important to the country's international competitiveness.
He said: "It really depends on how the Foreign Office implements the new system.
"If the vetting is restricted to a small number of countries that attract relatively few students, then the impact might be quite small.
"But if the scheme catches large numbers of students indiscriminately it could put people off coming to this country."
A spokesman for the Foreign Office said the scheme would require all foreign postgraduates who needed a visa and wanted to study in "proliferation-sensitive" subjects to apply in advance for a "clearance certificate" online.
This would affect some fields of biological and physical science, engineering, maths and computer science.
In 2005-06 some 124,000 postgraduate students came to study in the UK, 22,630 of whom studied in the fields affected - but not all in "proliferation-sensitive" areas.
The system will look at where the students come from, what they want to study and what they intend to do with the knowledge.
It will run alongside the existing visa system but those who are not given clearance are unlikely to be successful in their visa applications.
'Onus on us'
The Foreign Office spokesman added: "It's not my impression that this is a particularly large-scale problem here but there was an argument for putting it on a mandatory footing.
"We will have to weigh up the arguments but our objective is to ensure that students coming into the UK to study do not take back information that helps the spread of weapons of mass destruction at home.
"However, it would not be in anybody's interest to penalise bona fide students interested in coming to study here.
"The onus will be on us to make sure the system is not a long drawn-out process."
It was hoped it would take a couple of weeks in a non-complicated case.
The approval scheme website is currently being "road-tested" and could be up and running by the summer.
The review of the student vetting system comes after concerns were raised in 2002 about Iraqi researchers who applied to study at Oxford University.
They were later suspected of wanting to make bacteriological weapons resistant to standard antibiotics, arrested and returned to Iraq.
The Commons foreign affairs select committee then voiced concerns about the effectiveness of the student vetting system in such sensitive areas.
Committee member Andrew McKinlay said at the time: "I'm sure that there will be people in academia who will fling out their arms in horror about this - but to do nothing in my view is foolhardy and reckless in the extreme.
"Many of our postgraduate institutions are a soft underbelly."
Former academic and chairman of the science and technology select committee, Dr Ian Gibson, says the move is a "silly over-reaction".
"The result will be that many students from other countries, particularly those on the black list, just won't come.
"It would be a shame because I don't honestly think if there's someone who is a potential terrorist, that this is going to stop them."
Other countries were beginning to relax their approach to the issue, he added.
A spokeswoman for the Royal Society said it was clearly "a priority to prevent the proliferation of chemical, biological and nuclear weapons".
But it was important that any successor to the Voluntary Vetting Scheme did not dissuade potential postgraduates from applying to study in the UK by creating unnecessary hurdles in the application process.
"An overzealous replacement for the Voluntary Vetting Scheme could negatively impact the UK economy and its reputation as one of the most attractive places for students to study abroad," she added.