British Foreign Secretary William Hague on Thursday warned against the "selective application of the rule of law" in Russia following the jailing of protest leader Alexei Navalny.
"I am concerned about the sentence handed down by the Kirov court to Alexei Navalny," Hague said in a statement, after the 37-year-old Kremlin critic was found guilty of embezzlement.
"The decision to sentence him for five years has highlighted once again the concerns felt by many about the selective application of the rule of law in Russia."
Navalny emerged as a powerful new political force in mass protests against President Vladimir Putin, but he has now pulled out of elections for Moscow mayor and called for a boycott.
"We understand Mr Navalny intends to appeal this judgement," Hague continued.
"I call upon the government of Russia to respect fully the principles of justice and ensure that the rule of law is applied in a non-discriminatory and proportionate way."
Navalny was found guilty of defrauding the local government in the northern Kirov region of 16 million rubles ($500,000) in a timber deal while acting as an unpaid advisor to the local authorities.
He had dismissed the charges against him as absurd and a Kremlin set-up designed to end his political career.