MARGARET Thatcher considered restarting Britain’s chemical weapons (CW) programme at a cost of up to pounds sterling200m in response to Soviet threats, Downing Street correspondence reveals.

The prime minister, by training a research chemist, acknowledged that the government might be considered negligent for failing to acquire a “retaliatory capability” at the height of the cold war.

Secret papers canvassing the military options available have emerged from a Home Office file, released on Tuesday by the National Archives in Kew, which contains warnings that airborne chemical attacks by Soviet aircraft on sensitive UK targets could inflict massive loss of life.

One civil defence paper estimated that up to 140,000 people could be injured and more than 20,000 killed if Liverpool’s dockyards were hit by lethal gases. If Gatwick was struck, medical modelling suggested, there would be about 30,000 casualties and 16,000 dead.

File released by National Archives reveals PM examined how UK could retaliate in case of Soviet chemical attack

The UK had ratified the Geneva protocols in 1930, which banned the use of toxic gases and bacteria in war. But the treaty did not outlaw development or production of such weapons of mass destruction and permitted their use in retaliation.

The communist bloc’s expanding stockpile of nerve agents alarmed ministry of defence planners who warned that there was no military response short of escalating directly to nuclear conflict.

“Any significant step ... to improve our retaliatory capability will involve serious political and presentational difficulties,” a secret policy document admitted. Saddam Hussein’s use of sarin and other toxic agents in the Iran/Iraq war was seen as helpful in alerting the public to the threat.

In February 1984, the prime minister attended a CW briefing in the chief of staff’s room at the MoD along with the defence secretary, then Michael Heseltine, senior army and intelligence officers and the government’s chief scientific adviser.

“Nato has no capability to retaliate in kind, although the Americans have a small stockpile not declared to Nato,” civil servants reported. “The threat of nuclear retaliation in response to a chemical attack is our only deterrent and is not credible in all circumstances.

“MoD are currently considering proposals for issuing ... protective suits to UK-based servicemen and essential supporting staff. There is however little public awareness of the threat outside official circles, no civil defence plans are yet made against chemical weapons and no formal guidance has been issued.”

Another note recorded: “Chemical warfare is likely to be an emotional issue and any increase in public awareness is, if possible, best delayed until the general public can be given credible guidance on protection measures.”

Problems were anticipated. A policy document rated “Secret UK Eyes A” said: “A sharp turn in HMG’s policy on CW basing or acquisition, after 25 years of no direct involvement with such weapons, will provoke political controversy just when the public debate over the basing of cruise missiles is showing signs of declining.

“A unilateral UK move would create even starker problems of domestic and international presentation, particularly if such action were to contrast with continued congressional reluctance to fund modernisation.”

It observed that the military chiefs of staff believed the only effective and credible deterrent to Soviet use of chemical weapons was “the ability to retaliate in kind”.

Among retaliatory options proposed were offering “practical support to the US administration by permitting the forward basing of US delivery systems and storage of CW in this country in time of tension or even in peacetime. A variation would be to offer to provide delivery systems ourselves ...

“Finally there is the option of acquiring an independent UK retaliatory capability, based perhaps on American technology. The cost would be of the order of (pounds sterling)100m to (pounds sterling)200m. Such a decision would be a last resort should all other options fail.”

The file does not record the final outcome of deliberations but a letter from Charles Powell, Thatcher’s private secretary in Downing Street, recorded the outcome of a further, senior ministerial summit on chemical weapons in August that year.

The following decision had been made, Powell informed the permanent secretary at the MoD: “Modern NBC [nuclear, biological or chemical] equipment should be issued to servicemen and essential civilians in British forces Germany and to some 140,000 servicemen in the UK with a Nato role.”

He added: “The Americans should be encouraged to move forward with modernisation of their capability ... Public opinion in the UK could be brought gently to a better and wider perception of the imbalance between Soviet and Nato capabilities in chemical warfare while avoiding an upsurge of alarm.”

Assessing whether the UK should acquire an independent CW capability, attention was drawn to the drawback that “it might undermine the broader support which had been built up recently in public opinion for the UK’s role as a nuclear power.

“Summing up the discussion, the prime minister said that it might be argued that it was negligent of the government not to acquire a CW capability. But this was not a decision which could be addressed at this stage. Further discussions should be held with the Americans to discover more of their intentions and to encourage them to modernise their CW capability. These discussions should be on a bilateral basis rather than involving other Allies who were unlikely to have similar views.”

The UK did not sign the chemical weapons convention, by which participating countries agreed to destroy all CW capability, until 1993.

—By arrangement with the Guardian

Published in Dawn, December 31st, 2014