A former KGB agent turned author lost a high court battle for libel damages yesterday over an article about his book on Stalin-era espionage, published in 2000.

Alexander Vassiliev, from Harrow, north-west London, attempted to sue the publishers of the journal Intelligence and National Security over an article by British lawyer and filmmaker John Lowenthal.

London-based publishers Frank Cass contested the case.

Jurors found that the words complained of were defamatory but that they were an expression of opinion.

Mr Lowenthal's article was about Alger Hiss, a high-ranking official in the US state department who was accused of spying for the Soviets in the 1930s.

A debate has raged for years over whether Hiss, who was convicted of perjury in 1950, was a victim of a miscarriage of justice.

Mr Vassiliev says the book Haunted Wood: Soviet Espionage in America was based mostly on top secret KGB files.

Mr Lowenthal questioned the reliability of evidence that confirmed Hiss's conviction, suggesting that KGB documents had been "misconstrued".

Mr Vassiliev, who will have to pay costs, told the jury that he was in court to defend his reputation.