The prime minister said he "cannot see for the life of me" how relations with Putin could be "renormalised".

"Repentance is going to be very difficult for Vladimir Putin now," Mr Johnson told LBC.

It comes after the UK signed mutual security pacts with Nordic states Finland and Sweden.

Russia has warned Sweden and neighbour Finland, with whom it shares a lengthy land border, against joining defence alliance Nato, and has warned of "consequences".

    How do you join Nato?

Asked by LBC if Putin could ever be welcomed back on the global stage if he repents, the prime minister said: "Nothing is impossible, I suppose - but I just cannot see for the life of me how we can renormalise relations with Putin now.

"He [Putin] has grossly violated human rights, international law; he's guilty of absolutely barbaric onslaught on a totally innocent country - and to renormalise would be to make the mistake we made in 2014."

Vladimir Putin used his Victory Day speech to justify his attack on Ukraine
'Twisting the knife'

Mr Johnson, who agreed mutual security pacts with Sweden and Finland on Wednesday, warned against making the same mistakes made over the 2014 Russian annexation of Crimea.

"The world basically said, this is appalling: we condemn it, we denounce it - and we did. And we put on sanctions.

"But at the same time, we kind of opened negotiations with him about a way forward," he told LBC.

"And Putin basically used that as a way of twisting the knife in Ukraine."

"If the Ukrainians were to do any kind of deal with Putin now, the risk is that he would do exactly the same thing and they know it.

"So the short answer is no. No renormalisation - and the UK is very clear about that."

US intelligence has warned Putin is preparing for a long war in Ukraine, with even Russian victory in the east of the country - where fierce fighting continues - potentially not ending the conflict.

It comes as the UK has pledged an extra £1.3bn in military support to Ukraine as forces there push back the Russian invasion.