Leading neuroscientists believe that the UK Government may be about to sanction the development of chemical incapacitants for British police that would be banned in warfare under an international treaty on chemical weapons.

A high-level group of experts has asked the Government to clarify its position on whether it intends to develop "incapacitating chemical agents" for a range of domestic uses that go beyond the limited use of chemical irritants such as CS gas for riot control.

The experts were commissioned by the Royal Society, the UK's national academy of sciences, to investigate new developments in neuroscience that could be of use to the military. They concluded that the Government may be preparing to exploit a loophole in the Chemical Weapons Convention allowing the use of incapacitating chemical agents for domestic law enforcement.

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The 1993 convention bans the development, stockpiling and use of nerve agents and other toxic chemicals by the military but there is an exemption for certain chemical agents that could be used for "peaceful" domestic purposes such as policing and riot control.

The British Government has traditionally taken the view that only a relatively mild class of irritant chemical agents that affect the eyes and respiratory tissues, such as CS gas, are exempt from the treaty, and then only strictly for use in riot control.

But the Royal Society working group says the Government shifted its position to allow the development of more severe chemical agents, such as the type of potentially dangerous nerve gases used by Russian security forces to end hostage sieges. "The development of incapacitating chemical agents, ostensibly for law-enforcement purposes, raises a number of concerns in the context of humanitarian and human-rights law, as well as the Chemical Weapons Convention (CWC)," the report says.

"The UK Government should publish a statement on the reasons for its apparent recent shift in position on the interpretation of the CWC's law enforcement position." The Royal Society group points to a 1992 statement by Douglas Hogg, the then Foreign Office Minister, who indicated that riot-control agents were the only toxic chemicals that the UK considered to be permitted for law-enforcement purposes. But in 2009 ministers gave a less-restrictive definition suggesting the use of "incapacitating" chemical agents would be permitted for law-enforcement purposes as long as they were in the categories and quantities consistent with that permitted purpose.

Professor Rod Flower, a biochemical pharmacologist at Queen Mary University of London, said the latest scientific insights into human brain is leading to novel ways of degrading human performance using chemicals.