Peierls, who was born in Berlin in 1907, came to Britain in 1933. Together with his Birmingham colleague Otto Robert Frisch, he wrote the now famous "Frisch-Peierls memorandum", which warned the British government in 1940 that an atomic bomb could be built from relatively small amounts of uranium. Peierls later worked on the Manhattan nuclear-bomb project at Los Alamos between 1944 and 1945.

Farrell says in his Spectator article that Peierls was one of nine Soviet spies to infiltrate the project. He bases his claims on information from allied intercepts of messages sent to and from Moscow between 1940 and 1948. The messages (code-named Venona) remained top-secret until they were declassified in 1995. Farrell says that according to "British security sources" Peierls was the spy code-named both "Vogel" and "Pers". He also claims that "British and American security service sources...are convinced that" Peierls' Russian wife, Eugenia, whom he married in 1931, was another Los Alamos spy, code-named "Tina".

But in a letter in the 12 June issue of The Spectator, Peierls' daughter, Jo Hookway, flatly refutes the claims. She points out, for example, that although her mother had studied physics, she was not a nuclear physicist, as Farrell claims, and did not pursue a career in physics after her marriage: "[She was] a housewife...[and] security would not have allowed her so much as to enter a laboratory at Los Alamos." And while Farrell asserts that "Pers" was recruited as a spy in part because he felt he had been tricked into working on the bomb by being told that Germany was developing its own bomb, Hookway emphasizes that it was Sir Rudolf who warned the British government of the danger from Germany.

"My feeling is that it's wrong that a respected journal like The Spectator can publish an article so full of wrong facts. Apart from pointing out the errors, nothing can be done about what they have written," Hookway told Physics World magazine. "This incident is upsetting to everyone who knew my father, who was a well respected member of the physics community."

Farrell told Physics World that he based his article on information given to him by the military historian Nigel West, who has just written a book on the Venona texts entitled Venona: The Greatest Secrets of the Cold War (Harper Collins 1999). "West has been speaking to his military sources, who told him that Peierls was the best candidate for Vogel/Pers. I can't prove Peierls was a spy but I wouldn't have written the article if I didn't believe it," said Farrell. "But if it is a mistake, I deeply regret it." Indeed, in his book, West says that "whatever the truth, the mystery of Vogel/Pers remains unresolved, as does the true identity of Tina".

However, in a letter in the 19 June issue of The Spectator, West supports Farrell's original claims. "Jo Hookway may be distressed to learn that the Security Service and the FBI considered her father as a prime candidate for the Soviet spy code-named Pers," he writes. "The FBI and MI5...had good, if not legally conclusive, evidence that he had been linked to Soviet espionage." West adds that the vast scale of Soviet espionage inside the Manhattan project is "undeniable" and says that spies code-named "Quantum", "Solid", "Smart", "Erie" and "Huron" remain to be identified.

Peierls' son Ronald Peierls has called West's response "absolutely appalling and in some ways worse than Farrell's article".

Sir Rudolf was a widely respected physicist, who made seminal contributions to solid-state theory and to nuclear and elementary particle physics. He was awarded numerous prizes and medals, and was chairman of the Pugwash peace movement from 1970 to 1974.