THE Morning Star can reveal that MI5 declined to censor a book about its bugging of the British communists’ HQ, partly for fear of drawing the Soviet Union’s attention to the Security Service’s “sensitivity on the subject.”

In a letter — dated February 1968 and made public today by the National Archives — to Michael Stewart, the then Labour government’s first secretary of state, MI5 said it had “covertly” obtained a typescript copy of double agent Kim Philby’s memoirs.

It pointed out that, according to Philby, Roger Hollis — head of MI5’s F division, which monitored political groups — had the Communist Party of Great Britain’s (CPGB) office in central London under constant state surveillance.

Mr Philby’s book says: “Although Hollis had achieved little in respect of Soviet activity, he had been successful in obtaining an intimate picture of the British Communist Party by the simple expedient of having microphones installed in its King Street headquarters.”

MI5 said that the Foreign Office had notified prime minister Harold Wilson of the book passage. Mr Wilson then asked MI5 whether it still “operated eavesdropping devices against the headquarters.”

The letter, stamped “secret,” added: “The answer is that we do and the devices are very productive.”

MI5 then warned: “The publication of this passage may have various unfortunate consequences, including reminding the Communist Party of the possibilities of this kind of attack. 

“I therefore considered whether we should seek to have the passage deleted from the published version but decided against attempting this, both because it is likely to be published abroad and its suppression would draw the attention of the publishers and the Russians to our sensitivity on the subject.”

A microphone was discovered inside an office wall in 1975 during building work at the headquarters, a year before the CPGB sold the building. The device dated from the early to mid 1960s, according to a security expert. 

The CPGB eventually disbanded into groups, including the Communist Party of Britain (CPB).

CPB general secretary Rob Griffiths said: “This episode confirms that MI5’s primary concern was to conceal the vast scale of its clandestine activities from the general public.

“The Communist Party and Soviet intelligence was  largely aware of the Security Service’s routine bugging and phone tapping of party premises across Britain.

“The question is whether the public will ever be told about many other anti-democratic actions carried out by MI5, MI6, GCHQ and Special Branch against communists, socialists, trade unionists, civil liberties groups as well as peace and anti-apartheid campaigners.”