Britain's Foreign Secretary David Miliband says Russia's assault on Georgia shows it can't accept the Soviet Union era is over.
He told BBC radio that Russia was guilty of an act of "blatant aggression" against its neighbor.
Miliband says the political fallout from the conflict could include Russia's isolation from the Group of Eight industrialized nations. He is traveling to Brussels, Belgium, for talks on Europe's response.
The lawmaker told the BBC that the Kremlin had acted as if the Soviet Union had never disintegrated.
Relations between Russia and Britain have been strained in recent years, particularly after Alexander Litvinenko's poisoning. Russian emigres blame Moscow for the former KGB agent's unsolved death.