MOSCOW — The Russian government moved on Wednesday to defang efforts to stage antigovernment rallies this weekend by blacklisting the coordinator, Open Russia, an organization founded by the Kremlin critic Mikhail B. Khodorkovsky.

Although the main organization is based in Britain, Russia’s prosecutor general labeled it “undesirable,” effectively making it illegal for the body to operate inside Russia. It cited the protest efforts as the main reason.

Two other groups linked to Mr. Khodorkovsky were included in the ban. One, the Institute of Modern Russia, is run from the United States by Mr. Khodorkovsky’s son, Pavel, and the other, Open Russia Civic Movement, has headquarters in Britain.

“Their activities are aimed at inspiring protests and destabilizing the internal political situation, which threatens the foundations of the constitutional system of the Russian Federation and the security of the state,” the prosecutor general said in a statement.