Lessing was monitored over fears that her communist sympathies had been "fanned almost to the point of fanaticism," it emerged.

MI5 took a dim view of Lessing's communist beliefs and anti-racist activism. Between 1943 and 1964 the author's phone was tapped, her letters were monitored and she was followed on trips, according to files released Friday by Britain's National Archive.

The UK's domestic and foreign intelligence agencies amassed five volumes of files on the author, describing her visits to East Germany and Moscow during the Cold War at the invitation of the Union of Soviet Writers.

Suspicion of links to people with 'foreign accents'

Lessing, who was born to English parents in Iran in 1919, first came to the attention of intelligence agents in 1943 in the British colony of Rhodesia, now Zimbabwe, where she grew up.

She joined left-leaning groups including the Rhodesian Friends of the Soviet Union and also ran the Salisbury Left Club in Southern Rhodesia, a club "patronized by persons with foreign accents," the records show.

"The general tone of this club is reported to be very left, and it is stated that most topics of discussion there usually end up in anti-British, anti-capitalist and anti-imperialist vapourings," according to a note in her MI5 files.

Lessing was particularly critical about the poor treatment of black Africans.

"Her communist sympathies have been fanned almost to the point of fanaticism owing to her upbringing in Rhodesia, which has brought out in her a deep hatred of the color bar," records show.

"Colonial exploitation is her pet theme and she has now nearly become...irresponsible in her statements...saying that everything black is wonderful and that all men and all things white are vicious."

She joined the Communist Party during World War II and went on to marry German exiled communist Gottfried Lessing.

After her divorce from Gottfried, the author moved from Rhodesia to London in 1949, where security agents picked up her trail.

Several of Lessing's 1950s annual membership cards of the Communist Party of Great Britain feature in the file.

Spies continued to keep tabs on the author - who won the Nobel Prize for Literature in 2007 - in Africa and Britain until 1964.

Lessing, whose books include "The Golden Notebook" and "The Sweetest Dream," died in 2013 aged 94.

Doris Lessing won the Nobel Prize for Literature in 2007

Lessing's flat 'used for immoral practices'

One report provided to MI5 by the Special Branch of London's Metropolitan Police and dated January 1956 described her activist's lifestyle and contacts in suspicious terms.

"Her flat is frequently visited by persons of various nationality, including Americans, Indians, Chinese and Negroes," the report said.

"Some of the visitors seem to stay at the flat for days at a time and some of the visits are made by apparently unmarried couples," Special Branch noted, concluding: "It is possible that the flat is being used for immoral practices."

Files show that Lessing left the Communist Party later in 1956 in protest over its support for the crushing of the Hungarian uprising by Soviet forces.

Looking back on her years as a Communist Party member, Lessing said: "I can't understand why I was so gullible."

mh/kms (AFP, dpa, Reuters)