Vladimir Putin is so popular in Russia that he has the “political space” to withdraw his forces from Ukraine, said Boris Johnson.

       The prime minister said the Russian president still has “massive backing” from his own people despite international outrage over the invasion.

       “The Russian public overwhelming back Putin,” Mr Johnson told Talk TV. “Therefore he has the political margin for manoeuvre from within Russia … Putin has far more political space to back down, to withdraw.”

       The PM added: “There could come a point when he could say to the Russian people, ‘The military-technical operation that we launched in Ukraine has been accomplished’. He has a lot of room for manoeuvre.”

       Mr Johnson also said he did not expect Putin to use tactical nuclear weapons in Ukraine if he faced more military failures in the country – saying he was not worried about the scenario.

       Recommended Ukraine news – live: Russia bombs east as US promises new weapons Why has Russia invaded Ukraine? The conflict simply explained Sign The Independent’s petition to help the people of Ukraine

       He also rejected Moscow’s claim that the UK was engaged in a proxy war with Russia. “It’s very important we don’t accept the way the Russians are trying to frame what’s going on in Ukraine,” Mr Johnson said.

       The PM dismissed Sergei Lavrov’s comments about the increased risk a nuclear war, after the Russian foreign minister claimed Nato was “in essence” engaged in a proxy war by supplying Ukraine with weaponry.

       Earlier on Tuesday the Armed Forces minister James Heappey backed Ukrainian strikes on targets behind Russian lines – even if the weapons used have been supplied by the UK – saying it was “completely legitimate”.

       Mr Johnson said: “We don’t want the crisis to escalate beyond Ukraine’s border, but as James Heappey said, they have a right to defend themselves.”

       The prime minister said it was “quite extraordinary” that Sweden and Finland had said they wanted to join Nato – warning Putin that western nations would provide more weapons and share intelligence with Ukraine.

       He added: “I have a lot sympathy with individual Russians, with Russia as country – it’s a fantastic country. But Putin’s regime is engaged in a diabolical attempt to crush the life out of the Ukrainians.”

       The PM did not rule out a prisoner swap to free a Briton who has been captured by Russian forces but said his government could not “pre-empt” what decisions may be made by Ukraine’s leaders.

       The family of Aiden Aslin, who has been captured during the Ukrainian war, want Russia to free him after he appeared in a video asking to be part of a prisoner swap in exchange for pro-Russian politician Viktor Medvedchuk, held by Ukraine.

       On the chances of a prisoner swap, Mr Johnson said: “We will do what we can. Clearly it is for the Ukrainians. They have the other individual who is part of the equation. We can’t really pre-empt what they may decide.”

       Recommended Johnson says public deserve ‘faster, cheaper’ passport service UK’s ‘self-lacerating classes’ should be more confident: Australian diplomat Sexist Tory attacks on Angela Rayner ‘stink of classism’

       Mr Johnson said Mr Aslin and others were “entitled to rights under the Geneva Convention”, adding: “They should not be paraded in front of the cameras. They should not be made to give hostage videos – that is a breach of their rights as prisoners of war.”

       The prime minister said Facebook was removing a video clip of Mr Alsin comes after culture secretary Nadine Dorries called Nick Clegg, vice president of global affairs at parent company Meta.