University departments should expect to replace at least 10 per cent of their senior academics every year to make room for younger researchers, a conference heard.
Sir John Beringer, former pro vice-chancellor for research at the University of Bristol, told the Royal Society and Nature magazine conference, Tomorrow's Giants, that universities put young researchers under enormous pressure by assessing them continually. But he said that all the pressure was taken off once people gained senior positions.
"We need a system that works to weed out weak members of senior staff," he said. "Departments should expect a churn of 10 per cent or even 20 or 30 per cent per annum in less-good institutions. Without that, young people have little career progression because the old dogs hang around."
Professor Beringer was part of a panel responding to issues raised by young researchers at the conference last week. Principal among those was the lack of early career stability and permanent positions.
David Willetts, the universities and science minister, agreed that a structure was needed that allowed researchers to thrive when they were young and at their most innovative.
But Tony Hey, corporate vice-president of external research at Microsoft and a former dean of engineering and applied science at the University of Southampton, said researchers should accept that their chosen path had always been a "precarious lifestyle". He said: "When I was dean I resented paying lip service to giving postdocs job certainty."
Dame Wendy Hall, professor of computer science at Southampton, said there needed to be a better mechanism for supporting promising young researchers to take risks.
"Tomorrow's giants are today's pioneers," she said. "But it is a real struggle at the beginning and a lot of people fall by the wayside."
She said her own early research had been possible only because a professor had supported it.
There were also complaints about the amount of time researchers were obliged to spend on grant applications and outreach activities.
"Sometimes principal investigators long to be postdocs again so we can do the job we are good at," one delegate said. "Tomorrow's giants should be people who can do great science, not ones who can sell it."
Dame Sally Davies, chief scientific adviser for the Department of Health and the NHS, admitted that she was "stuck and worried" by the complaints.
But Adrian Smith, director general of science and research at the Department for Business, Innovation and Skills, said scientists had a responsibility to remember that their funding came largely from the taxpayer. "You won't have an environment where people want to spend a lot of money on science unless there is communication," he said.
Delegates were also concerned about a lack of core technical support and the scarcity of permanent positions for research assistants. Professor Beringer said universities were free to hire permanent research assistants but usually preferred to recruit an extra academic.