Foreign Secretary David Cameron said:
Two years on from Vladimir Kara-Murza's arrest on fabricated charges, I urge the Russian authorities to release him immediately on humanitarian grounds.
A committed human rights activist striving for a democratic Russia, and an outspoken critic of the war in Ukraine, Mr Kara-Murza was considered a threat by the Kremlin. Putin locked him up in a bid to silence him.
We must call out Russia's callous disregard for his declining health. The victim of two separate poisoning attempts prior to his imprisonment, Mr Kara-Murza is now being subjected to degrading and inhumane conditions in prison, clearly designed to further damage his physical and mental well-being. He has been refused the urgent medical treatment he so desperately needs.
Through diplomatic interventions at the highest levels, financial sanctions targeted at those behind his poisoning and imprisonment, and by raising his case on the international stage, we are sending a clear message that the UK will not stand for this abhorrent treatment of one of our citizens.
Russia's depraved treatment of political prisoners must end.
