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Aleksandr Solzhenitsyn's cantankerous side is exposed in a letter he sent to The Times in 1974, the year of his expulsion from the Soviet Union, that was never published in English because of its controversial content.

The letter, consisting of two closely typed pages in Russian, survives in this newspaper's archive, alongside the dissident's hand-written envelope.

Solzhenitsyn, who died on Sunday, wrote in his characteristic emotionally charged tone to vent his outrage at Zhores Medvedev, a fellow exile who became famous for exposing a serious nuclear accident in the Ural mountains in the 1950s.

The dissident, writing from his new home in Zurich, accused Dr Medvedev of being an apologist for the regime and of making public statements that served the Soviet empire better than the “whole Soviet propaganda apparatus”.

But Dr Medvedev, 83, told The Times this week that Solzhenitsyn's accusations were “absolute rubbish” and that the slurs were typical of an egotistical man who habitually cut off his friends when they ceased to be useful to him.

Speaking at his home in Mill Hill, northwest London, Dr Medvedev said that the letter was designed to generate a public row so that the world would know they were no longer friends.

“It is not anger,” he said. “It is cold calculation - a normal episode in which I was insulted a little. I did write a book about him. Everybody knew that we were friends, so it would be unnatural for us to stop talking. So if he wanted to cut [communication], he would have to do something cruel.”

Solzhenitsyn claimed that his friend had made a “mockery of the truth” by declaring, in a radio interview a year earlier, that using the term “Soviet regime” was an unfair slur on the Soviet Union's elected government.

Solzhenitsyn also alleged that Dr Medvedev had announced that Soviet authorities no longer punished dissidents by declaring them insane and committing them to lunatic asylums,- a ploy used against Dr Medvedev himself. Dr Medvedev denies saying the words attributed to him.

The final charge levelled at Dr Medvedev was that he failed to support the Nobel Prize nomination of Andrei Sakharov, the scientist who helped to build the Soviet Union's first hydrogen bomb but later became an outspoken humanitarian.

Solzhenitsyn claimed that Dr Medvedev, while attending the Nobel Institute in Norway, said: “You must analyse and weigh up how great a contribution Academician Sakharov made to the cause of peace and how great - to kindling the flames of war.”

Dr Medvedev admits that he chose not to drum up support for Sakharov, who won the prize a year later in 1975, but never used the expression “kindling the flames of war”. He said that he had been warned by the institute that it was customary not to discuss prize candidates and so gave a cautious reply when asked about Sakharov at a public event. “I was in a difficult situation. I said, 'He is a good candidate, but I am not in a position to judge the others'.”

The Times, to Solzhenitsyn's irritation, refused to print the letter unless the author could provide evidence that he had quoted Dr Medvedev accurately. The dissident, who was then at the height of his fame, angrily declined and sent the letter to Aftenposten, a Norwegian newspaper, and a Russian-language newspaper based in Paris. The letter appeared in both publications, but it was never published in English.

Dr Medvedev was resigned to being rejected by Solzhenitsyn. “I knew sooner or later it would happen. [I] was cut from his circle like others before. It is sad. He died, unfortunately, without a single friend. He was absolutely isolated. He didn't have anyone who came to discuss politics with him.”

Solzhenitsyn even fell out with Aleksandr Tvardovsky, the editor who persuaded Nikita Khrushchev, then the Soviet premier, to allow the publication of One Day in the Life of Ivan Denisovich, the novel that exposed the horror of Soviet labour camps and made Solzhenitsyn's name.

Dr Medvedev recalled that Solzhenitsyn also snubbed Mstislav Rostropovich, the world-renowned cellist who sheltered Solzhenitsyn at his dacha for three years when the writer was being victimised by the Soviet state.

Rostropovich defected but became stuck in Paris when his attempt to enter Britain was delayed because Customs officials refused to grant entry to his beloved dog.

Desperate for money, Rostropovich called his friend Solzhenitsyn, by now a multimillionaire from sales of his books, to ask for a loan. Solzhenitsyn would not take or return the cellist's calls.

On another occasion, Solzhenitsyn refused to attend a dinner at the White House given by President Ronald Reagan in honour of Soviet dissidents because he objected to the calibre of some of the other guests.

“He was a difficult man,” Dr Medvedev said.

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