The Particle Physics and Astronomy Research Council has decided to penalise physics departments in which students take longer than average to submit their PhDs. But British physicists have warned that it could lead to PhDs being worth less than their international counterparts.
"There is a danger of PhDs getting squeezed at both ends: we are being asked to teach more transferable skills at the start and finish earlier," said Roger Cowley, head of physics at the University of Oxford.
"If the PhD got thinner I would be very concerned about the position of a British student compared with those trained in Germany and France."
A senior physicist who did not wish to be named, added: "If you wish to guarantee that a student will finish in a set time, you need to set a less ambitious project.
"The international community knows what a PhD is, and I do have worries that quality will suffer. We will be given the choice between a good thesis and a thesis submitted on time."
Physics has long had a problem with the length of time it takes to get a PhD. Just 13.5 per cent of students who started their PhDs in 1993 had completed them in the three years for which they are funded, with 80 per cent completing in four years.
PPARC plans to withhold the allocation of student numbers from departments that take longer than average to submit. However, Steve Cann, of PPARC's education and training section, said that cuts would be limited to 10 per cent for the next allocation for places starting in 2000 and 2001.
While most physicists support the idea of encouraging students to submit on time, they are appalled at the idea of being penalised for students who take longer than average.
"The system needs to be more flexible," said Malcolm Longair, head of physics and astronomy at the University of Cambridge.
"For example, the weather could be bad, affecting observations - that is not under the control of the supervisor," said Mr Longair.
Professor Cowley said students fail to write up for a variety of reasons that have more to do with the individual than with the department.
"For example, a student might disappear for a few months because his parents are getting divorced.
"Departments should ensure that students complete in time, but to penalise a department that doesn't manage to get its students to complete in four years is unreasonable - it is formulae going mad," he said.