MI6 wanted to mount a violent Cold War campaign of subversion and black propaganda to undermine the Soviet Union, according to official files made public today.

Tactics proposed ranged from minor disruption - throwing "stink bombs" at Communist Party meetings - to the "liquidation" of selected individuals in Russia and its Eastern Bloc allies .

However the plan was blocked by anxious Foreign Office officials who feared the consequences of such extreme methods.

The scheme was drawn up by MI6 chief Stewart Menzies following a call by military chiefs in 1947 for "a comprehensive political warfare plan which would include the use of both special operations and deception" to counter the growing Soviet threat.

In his paper, dated January 20, 1948, Mr Menzies proposed a range of actions starting with "minor acts of sabotage and intimidation" such as "throwing ridicule" on Russian personalities and institutions, and distributing forged ration cards, passes and currency.

Moving up the scale he suggested could involve sending "explosive parcels", causing accidents to Russian military trains and "incendiarism", starting "accidental" fires.

Finally, at the most extreme end, Mr Menzies proposed the "liquidation of selected individuals".

This could involve: "The 'framing' of diplomats and other officials by planted evidence, 'indiscreet' telephone calls, etc in order to effect their removal and possible liquidation."

Alternatively, he suggested the "kidnapping of high-ranking communist personalities or Russians in such a manner as to give the appearance of defection".

Mr Menzies warned: "Whereas certain types of clandestine propaganda may sometimes be attributed to HMG without undue harm being done, special operations of a violent or subversive nature must in peace always be 'unacknowledgeable' and HMG must in no way be implicated."

The Foreign Office was horrified, and at a meeting on February 13, 1948 it was made clear that most of the proposals were non-starters.

Nevertheless, it did accept there was a role for the "clandestine dissemination of oral and written propaganda" and agreed to the setting up of a black propaganda unit - the innocuously named Information Research Department.

Belfast Telegraph