A former FBI agent who failed to tell his superiors about an affair with an informant later arrested as a double agent for China was sentenced on Monday to three months' home confinement.

Retired FBI agent James J. Smith is seen in this July 8, 2003 file photo outside federal courthouse in Los Angeles. [AP] 

The sentencing of James. J. Smith was a low-key conclusion to a case that started as a high-profile prosecution of a supposed spy and ended with the dismissal of all charges against the main defendant.

Smith pleaded guilty in May to lying to the FBI about his adulterous 18-year affair with FBI informant Katrina Leung. Leung, who was known as "Parlor Maid," was arrested in 2003. Prosecutors portrayed her as a double agent for China, but she was ultimately charged only with taking classified documents from Smith.

The charges against Leung were thrown out in January by a federal judge who cited "willful and deliberate misconduct" by prosecutors. Prosecutors barred Smith from talking to defense lawyers, depriving Leung of a critical defense witness.

The news of Leung's arrest and lengthy affair caused a sensation in Los Angeles, where she was a prominent businesswoman, society hostess and political activist.

Smith, who worked for the FBI for almost 20 years, was also ordered to perform 100 hours of community service. His sentence was lighter than the two months in prison requested by federal prosecutors.

Editor: Yan