Russia’s lower house of parliament Friday stripped a leading anti-Vladimir Putin deputy of his mandate, in an unusual move critics said was revenge for his scathing criticism of the Kremlin.

Russia's lower house of parliament Friday stripped a leading anti-Vladimir Putin deputy of his mandate, in an unusual move critics said was revenge for his scathing criticism of the Kremlin.

The State Duma voted 291 in favor with 150 against and three abstentions to strip “A Just Russia” party member Gennady Gudkov of his mandate over alleged conflicting business interests.

Gudkov ejection had been in little doubt given it was supported by the dominant United Russia party.

"We have shamed ourselves today in front of the whole world," Gudkov told reporters after the vote, saying he would appeal the decision at the Supreme Court.

Russia's Investigative Committee is now examining whether he broke the law through his ownership of a private security firm while sitting as an MP. It will decide by September 23 whether to open a criminal probe.

After losing his mandate, Gudkov no longer has the immunity enjoyed by deputies and could in theory face criminal charges.

Gudkov was an agent at the Soviet secret service the KGB and its post-Soviet successor the FSB. He left the FSB in 1993.

He started a career in the parliament in 2001. He gradually became one of the Kremlin's most vocal critics in the Duma.