How Thatcher's election win launched secret war on CND

An army intelligence unit was used to infiltrate civil rights groups and protest organisations after Margaret Thatcher came to power. Former soldiers claim that they were ordered to undertake the spying missions by a senior officer in the Ministry of Defence.

The activities of 20 Security Company (V) after the Tories won the 1979 election had not hitherto been revealed. Some of its members have now spoken for the first time about how the military was used against civic organisations such as the Campaign for Nuclear Disarmament and Peace Pledge Union.

The revelations about the secret war against those regarded as "the enemy within" – including the use of agent provocateurs – comes at a time of increased interest in the Thatcher years with the release of The Iron Lady, starring Meryl Streep, today.

The instruction to 20 COY, a Territorial Army body which had focused on Northern Ireland, the Middle East and the British Army of the Rhine, came in a memo from a General in September 1979: "The change of government provides an excellent opportunity for the unit to play a more active role and to provide information about groups whose activities and interests are not beneficial and are opposed to the armed forces. The unit is well placed to do this because its members are civilians."

An operations room was set up at a building in north London. A former sergeant with the unit said: "The ops room's desks and walls were strewn with political newspapers, newsletters and leaflets, card collation files and annotated street maps. Those targeted were pacifists, anti-arms trade, anti-nuclear, radical and socialist organisations. So you had groups like the Peace Pledge Union, Troops Out and CND branches.

"Most of the meetings of these groups were held conveniently nearby in London like Hackney, Holborn, Camden and the well known King's Head pub in Islington."

Some of the undercover soldiers became officials in the organisations they had infiltrated, one being elected membership secretary. The former sergeant said: "On one occasion one of them was chanting anti-military slogans with a crowd opposite the entrance to the Royal Tournament at Earl's Court, while slipping away periodically to the 20 COY office inside to give updates. One hesitates to use the word 'provocateur'."

Stella Rimington, the former head of MI5, acknowledged after leaving the service that there had been "over-enthusiasm" in targeting left-wing groups during the early Thatcher years. "Files were opened on people who were not actively threatening the state."

Another former soldier of 20 COY, who now lives outside England, told The Independent: "We knew that MI5 and SB [Special Branch] were doing all kinds of things at the time. But the difference is that we were the Army, we were happy to go on undercover ops in Northern Ireland where there was a genuine terrorist threat. It simply wasn't our business to be spying on fellow citizens simply because the government did not like them.

"The thing is there were some senior people in the forces at the time who were very right-wing and they thought that Thatcher coming in gave them carte blanche to get up to all sorts of things. We heard whispers that some of these people were trying to destabilise Labour before the Tories got back in."

Sir Martin Furnival Jones, one of Ms Rimington's predecessors at MI5, had revealed that a plot against Harold Wilson's government involved senior civil servants and military officers, and the name of a major-general was given to the then Home Secretary, later Prime Minister, James Callaghan. No one was prosecuted. "They were" said Sir Martin, "a pretty loony crew."