British agency concluded that actor – described by US counterparts as 'parlour Bolshevik' – was no security risk

MI5 opened a file on Charlie Chaplin while he was being hounded by J Edgar Hoover's FBI for alleged communist sympathies.

The FBI, which described the star of Modern Times and The Great Dictator as one of "Hollywood's parlour Bolsheviks", asked MI5 for information to help get him banned from the US. The results, including information gathered through eavesdropping, are contained in an extensive personal MI5 file released on Friday at the National Archives.

"Chaplin has given funds to communist front organisations … He has been involved in paternity and abortion cases," an MI5 liaison officer in Washington warned in October 1952.

MI5 noted that a decade earlier Chaplin had told the Los Angeles branch of the National Council of American Soviet Friendship: "There is a great deal of good in communism. We can use the good and segregate the bad."

Papers have been withheld from Chaplin's MI5 file to protect the names of informants though there are unexplained, probably inconsequential, references to Jimmy Reid, the communist Scottish trade unionist; Larry Adler, the harmonica virtuoso who left his native US where he was branded a communist and blacklisted; and Humphrey Lyttelton, the Eton-educated jazz musician who once described himself a "romantic socialist".

MI5 intercepted a telegram from Ivor Montagu, a film critic, producer and one-time Soviet spy, telling Chaplin how sorry he was to miss him in London when the star visited London in 1952.

The file also contains cuttings from newspapers and magazines. Noting that Chaplin had not taken American citizenship though he had lived in the US for more than 30 years, the Daily Worker welcomed him to London. "His films have lampooned the great and the dictators, raised up the common man against the rich," the paper said. "Now the world's bully threatens the world's clown."

The FBI, which amassed more than 2,000 pages on Chaplin, asked MI5 if he was going to meet any "highly placed persons" in London, and to establish any links he had with the Communist party there.

In particular, it wanted MI5 to find out where Chaplin was born and pursue suggestions that his real name was Israel Thornstein.

MI5 searched but to no avail. There was "'no evidence that Chaplin's name is or ever has been Israel Thornstein", it told the FBI. A suggestion that he "may have been born in France" came to nothing.

MI5 found no record of his birth in Somerset House, then the home of the register of British births. "It would seem that Chaplin was either not born in this country or that his name at birth was other than those mentioned," an MI5 report concluded. It told the US that there was "no trace in our records of Charlie Chaplin".

It had always been assumed that Chaplin was born in Walworth, south London, on 16 April 1889. Recently, however, a letter was discovered in family papers from Jack Hill, who told Chaplin in the 1970s that he had come into the world "in a caravan [that] belonged to the Gypsy Queen, who was my auntie. You were born on the Black Patch in Smethwick near Birmingham."

The newly released file shows that while communist sympathies were the determining factor for the FBI, for MI5 the issue was whether Chaplin ever presented a security risk. And in its view, it makes clear, he was not.

"We have no trace in our records of this man, nor are we satisfied that there are any reliable grounds for regarding him as a security risk," Sir Percy Sillitoe, then head of MI5, told the chief police commissioner in South Africa, where Chaplin was planning a visit.

MI5 suggested his name had been exploited in the interests of communism as "one of the victims of McCarthyism".

Files previously released at the National Archives reveal that shortly before his death in 1950, George Orwell handed a female friend working for an anti-communist propaganda unit in the Foreign Office a list of 35 names of people, including Chaplin, whom he considered "crypto-communists and fellow-travellers".

Chaplin's MI5 file, number PF710549, concludes: "It may be that Chaplin is a communist sympathiser but on the information before us he would appear to be no more than a 'progressive', or radical."

In 1953 the US prevented Chaplin from returning to America. He denied ever being a communist but decided not to contest the US ban and instead live in Switzerland. "I am a victim of lies and vicious propaganda," he said.

Chaplin died in his sleep in Vevey, Switzerland, on Christmas Day in 1977.