David Kelly's death is a serious setback in the campaign to uncover the full extent of Iraq's illegal biological weapons programme, senior weapons experts believe.
Biological weapons and arms-control specialists fear Dr Kelly's suspected suicide will also damage future attempts to control the spread of biological weapons among rogue states and terrorists.
Academics and scientists closely involved in helping draft new, tougher international treaties on chemical and biological weapons said their senior defence and intelligence contacts now refuse to share information on arms-control issues - because Dr Kelly's treatment and death have sent shock waves throughout Whitehall.
Professor Julian Perry Robinson, a chemical weapons expert at Sussex University, said: "The willingness of people inside the system to talk to people outside the system has taken a definite turn for the worse. They're looking over their shoulders to an extent, which they weren't before."
The most immediate impact of Dr Kelly's death is the loss of his unparalleled expertise on Iraq's bio-warfare programme. The other world-leading authority on Iraq's bio-warfare programme, Richard Spertzel, is now in his seventies and retired.
Dr Kelly led the UN's original investigations into Saddam Hussein's weapons programme in 1992. He was due to fly out last month, days after his death, to help lead the UK section of the Iraq Survey Group - the US-led coalition inspection team trying to unearth evidence of Saddam's weapons programme.
It would take several junior inspectors weeks to research evidence or witness statements that Dr Kelly would immediately be able to evaluate, former colleagues said.
"His loss is a serious setback - no question about that," said Terry Taylor, a former Ministry of Defence arms expert who is now US director of the International Institute of Strategic Studies and who has worked closely with Dr Kelly.
That view was shared by Ewen Buchanan, spokesman for Unmovic (United Nations Monitoring, Verification and Inspection Commission). His experience would "certainly be missed", Mr Buchanan said. "He was intimately aware of all the ins and outs of Iraq's bio-warfare programme. No one else in the UK can match that knowledge."
Dr Kelly also briefed arms-control experts, government officials and international legal bodies on his experience in Iraq and in uncovering Russia's illicit and highly advanced bio-weapons programme in the early 1990s.
His colleagues fear the shock of Dr Kelly's death will lead many intelligence and defence officials to suspend contacts with experts outside the Government, or be much more cautious about discussing arms-control issues.
Dr Malcolm Dando, who runs a global programme at Bradford University to draft a new bio-warfare treaty, said this could directly undermine attempts to formulate a new biological and toxic weapons treaty in 2006. "My fear is that it's going to make it much more difficult to have the kind of transparency we need," he said.Reuse content