London, England (CNN) -- A British soldier who went absent without leave rather than return to fight in Afghanistan was jailed Friday for nine months by a military court, officials said.

A Ministry of Defence spokesman confirmed that Lance Corp. Joe Glenton had been convicted by a military judge at a court martial in Colchester, southeast England,

Glenton, who completed a seven-month tour of duty in Afghanistan in 2006, became an outspoken critic of British military operations in the country during his absence, frequently appearing at anti-war rallies and on television.

In an interview last July, the 27-year-old told CNN that he was not a conscientious objector, but was refusing to return because he felt the 2001 invasion and subsequent conflict against Taliban militants was not a legitimate use of force.

"The situation in Afghanistan and our involvement is further antagonizing the Muslim population of the world," Glenton said.

"I think the conflict has become part of the problem, not part of the solution."