One of Russia’s president, Vladimir Putin’s biggest critics, Vladimir Kara-Murza has been jailed in Russia for 25 years after being found guilty of treason.

Kara-Murza, 41, a father of three and former journalist who holds Russian and British passports, spent years as a politician opposing Putin.

He was accused of treason and of discrediting the military by prosecutors after he criticised the country’s invasion of Ukraine.

However, Kara-Murza, has criticised his prosecution, comparing it to one of Soviet dictator Josef Stalin’s show trials in the 1930s.

The opposition leader, who claims to have twice been poisoned by Russian secret agents, declined to ask the court to acquit him and said:

“Criminals are supposed to repent of what they have done. I, on the other hand, am in prison for my political views.”

“I also know that the day will come when the darkness over our country will dissipate,” he said during his trial.

Kara-Murza had used speeches in the United States and across Europe to accuse Moscow of bombing civilian targets in Ukraine which the Kremlin has denied.

He also claimed Russia was being run by a “regime of murderers” in a CNN interview, broadcast hours before his arrest.

His 25-year sentence, which matches the sentence requested by prosecutors, is the harshest of its kind since Russia invaded Ukraine.

Under censorship laws, introduced in the wake of Russia’s invasion of Ukraine, “discrediting” the army can currently be punished by up to five years in prison.

Spreading information deemed deliberately false about the Russian military can also attract a 15 year jail sentence.

Investigators added the treason charge, which carries a sentence of up to 20 years in Russia, while he was in custody.

Kara-Murza, who was once deputy leader of the opposition group People’s Freedom Party, is the current vice chairman of the pro-democracy and human rights group Open Russia.

He was an ally of the late Russian opposition politician Boris Nemtsov, who was shot dead near the Kremlin in 2015.

Kara-Murza and his supporters say he has twice survived being poisoned in the past – once in 2015 and again in 2017 .