By Lucy Papachristou

LONDON (Reuters) – Western governments and Russia’s exiled opposition should begin laying the groundwork for Russia’s democratic transition after President Vladimir Putin eventually leaves office, Vladimir Kara-Murza, a Russian opposition politician, said on Friday.

Seven weeks after he was released from a Siberian penal colony in a historic East-West exchange, Kara-Murza did not say how he thought Putin would leave, but argued Russia must not squander what he said would be a narrow sliver of time to establish a democratic government, as he said it did after the Soviet Union’s collapse in 1991.

“We need to learn from those past mistakes, from those past lessons, to make sure we do not repeat these failures the next time a window of opportunity for change in Russia opens,” Kara-Murza told reporters at the Royal United Services Institute, a London think tank, in his first public appearance in Britain since he was released on Aug. 1.

“None of us knows exactly when, exactly in what circumstances, but it’s going to happen in the very foreseeable future. And next time, we must get this right.”

Putin, 71, has been in office as president or prime minister since 1999. He began a new six-year term as president in May and dominates the political landscape in Russia, with leading opposition figures in prison or in exile.

Kara-Murza, 43, has emerged as one of the most prominent opposition voices in exile since his release from prison, where he was serving a 25-year treason sentence for publicly opposing the war in Ukraine. He holds Russian and British passports.

“Vladimir Putin must not be allowed to win this war in Ukraine. More than that, he must not be allowed to have a face-saving exit from this war,” he said on Friday.

He argued the West should be preparing a roadmap for a future democratic Russia, which should include Western leaders communicating to the Russian people that the West stands with them against Putin, Kara-Murza said. Securing the release of more prisoners of conscience – who he said number about 1,300 in Russia – is key.

“I wake up every morning and I go to sleep every night thinking about all the others who are still left behind,” the politician said. He cited 63-year-old Alexei Gorinov, the first person jailed under Russia’s wartime censorship laws, and Maria Ponomarenko, a Siberian journalist currently on hunger strike in prison, as among those in dire need of support.

(Reporting and writing by Lucy Papachristou; Editing by Frances Kerry)