MOSCOW — Russia’s Parliament voted to strip an opposition leader of his seat Friday, leaving him vulnerable to criminal prosecution in what his supporters describe as another step toward silencing criticism of President Vladimir Putin.
Gennady Gudkov, a 56-year-old former KGB officer who emerged in recent months as an advocate for the rule of law and freedom of speech, was accused of illegally running a business while serving in the State Duma. He called the charge politically motivated.
The expulsion of Gudkov, a lonely voice of criticism in the legislature, fit a pattern of measures aimed at curtailing protest after Putin’s return to the presidency in May after four years as prime minister.
‘‘This is a political revenge, extrajudicial reprisal,’’ Gudkov said, ‘‘carried out upon command from the Kremlin.’’
Gudkov is a member of the Just Russia party, which was formed in 2006 as an ostensible alternative to Putin’s United Russia party.
Serious opposition parties have been kept out of Parliament through manipulation of election laws, and until recently the Just Russia party operated more as a Kremlin ally than opponent. But last winter, as demonstrators took to the streets to protest vote-rigging and limits on democracy, Gudkov unexpectedly took up their cause.
Those protests, the first serious demonstrations against Putin since he took power in 2000, clearly rattled him. First he blamed the United States, claiming it financed the marchers, who he said were called out by a signal from Secretary of State Hillary Rodham Clinton.
If the protest angered Putin, it awakened something in Gudkov. He began speaking at protest rallies, embracing free elections and more robust democracy. But, as Putin’s critics saw it, even the rare public gadfly was one too many.
Gudkov soon came under investigation. In July he was forced to sell his security company, which he started before he entered the Duma in 2001. Then prosecutors asked the Duma to strip him of his seat and parliamentary immunity.
The vote to remove him Friday was 291 to 150.