Kalejs, who was identified last month as living in a retirement home in central England, allegedly served as an officer in Latvia's notorious Arajs Kommando unit.

The militia is held directly responsible for the deaths of 100,000 civilians, including 30,000 Jews, between 1941 and 1943.

Efraim Zuroff, head of the Israel office of the Simon Wiesenthal Center, said he regards the British decision not to try Kalejs as a "missed opportunity for justice."

Zuroff had earlier called on the Latvian government to seek his extradition, noting that Latvia had not previously tried war crimes suspects since it gained its independence, while it had indicted nine Communists for alleged Soviet-era crimes.

Kalejs has described his accusers as "liars and storytellers" and insists that he had been a student throughout the war.