The use of weapons of mass destruction by terrorists or national governments could damage international treaties and regimes designed to prevent their proliferation and use, a leading academic has warned.

Ahead of a meeting of leading American and European defence analysts and civil servants, Professor John Simpson called on the government to consider the impact of a WMD attack.

Simpson, an expert from the University of Southampton, says the international community must consider what would happen to regulatory and verification regimes if terrorists or national governments launched an attack.

"Weapons of mass destruction regimes are themselves already under strain as a consequence of the muscular and often unilateral approach to WMD control taken by the current US administration," he said.

"This has opened visible differences between the US and European approaches to these issues. It is not clear whether the use of WMDs would open the gaps still further, or lead to a consensus on the need to join ranks to address a common threat, as happened after 9/11."

This week's conference, organised by the International Institute of Strategic Studies, will discuss whether the definition of weapons of mass destruction should be expanded to include possession of missiles as well as nuclear, radiological, biological or chemical weapons.

"A key distinction in examining impacts upon a [weapons] regime may be between 'technical' breaches of its rules, and actions which breach the norms underpinning it," added Simpson.

"The latter clearly constitutes a challenge to the foundations of a regime and are thus likely to generate a radical response to prevent the regime suffering a serious loss of confidence: the former may create more opaque situations which are likely to lead to a response within existing regime boundaries."