A former KGB colonel turned opposition lawmaker who has angered the Kremlin with his scathing criticism and involvement in street protests against President Vladimir Putin was stripped of his parliament seat on Friday.

Gennady Gudkov's removal from the lower house paves the way for similar action against other opposition lawmakers, sending a clear message to members that they serve at the pleasure of the Kremlin.

The 293-150 vote with one abstention to expel Gudkov from the State Duma also means he will no longer be protected by immunity from prosecution. His supporters fear he could face arrest.

Gudkov denounced the move as "political revenge and extrajudicial repression."

Gudkov, like Putin a KGB veteran, is not your typical Russian protester. This 56-year-old stout, moustached man cut a striking figure among young activists as he chanted "Putin, Resign!" from the stage at opposition rallies last winter.

That was on weekends. During the week, he donned expensive suits and attended close-door meetings at the Russian parliament. He was deputy chairman of Parliament's security committee and enjoyed good relations with many senior officials in Russian police security agencies.

Thrown out before rally

The vote to expel Gudkov comes a day before the first major opposition rally after a summer break, a clear signal that the Kremlin is ready to toughen its stance against the opposition.

Gleb Pavlovsky, a former Kremlin political consultant, said it moved against Gudkov out of fear that his example might encourage other members of the ruling elite to join the opposition.

Gudkov's behaviour was like "a spectre of the split in the elite that the Kremlin is so afraid of," Pavlovsky said. "It scared them a lot."

For most of the past 10 years, the State Duma, the lower house, has obediently rubber-stamped all Kremlin bills. Critics were tolerated because a solid pro-Kremlin majority could ensure the safe passage of any legislation.

Gudkov, who worked in the KGB from 1981 to 1992 and then continued his career in its main successor agency, became a lawmaker in 2001. He initially was a member of United Russia, the dominant Kremlin party, before moving in 2007 to Fair Russia, another Kremlin-created party that has leaned more toward the opposition in recent years.

Stanislav Belkovsky, a political analyst who has had close government links, said the Kremlin has seen Gudkov as a turncoat who needs to be punished.

"For many years, Gudkov has been integrated in Putin's system of government and Putin's system of business," Belkovsky said on Ekho Moskvy radio. "Putin does not forgive treachery."

'Putin does not forgive treachery.'—Political analyst Stanislav Belkovsky

The onslaught against Gudkov and other opposition leaders began after a May 6 rally, which ended in clashes between protesters and police. The protest was on the eve of Putin's inauguration and the start of his third term as president.

The authorities started by launching an inspection of a private security firm that Gudkov set up when he left the security agency and revoked its license, citing purported irregularities. Then investigators and prosecutors sent petitions to parliament claiming that Gudkov was running a separate business, a market for construction materials, in violation of Duma regulations, and thus should be stripped of his seat.

Gudkov and his son, Dmitry, also a parliament member, rejected the charges and struck back by unveiling documents showing property and businesses owned by United Russia members, raising the question of why pro-Kremlin deputies face no such scrutiny.

Pressure on all lawmakers

Gudkov said that an attempt to strip him of his seat without any charges filed violated the law.

"If the parliament votes for that, it will mean that Russia has no parliament," he said.

Communist deputy Vladimir Pozdnyakov said he sees the likely expulsion of Gudkov as putting pressure on all lawmakers. "We have no guarantee now that any other deputy will not end up in this meat grinder," he said.

"They're expelling me from the Duma because they're afraid of the truth, afraid of criticism and my stance," Gudkov said. "We have come very close to the brink that separates an authoritarian regime from a dictatorship," he said.