Boris Johnson has said the West must continue to support the Ukrainians as they seek to recover territory seized by Russia, saying it would be a “catastrophe” if president Vladimir Putin was able to claim victory.

Speaking on his return to the UK after an unannounced visit to Kyiv, the Prime Minister said Ukraine should not be encouraged to accept a “bad peace” which would simply be the prelude to a renewed Russian offensive.

Mr Johnson also defended his decision to pull out of a conference of northern Tories on Friday, so he could meet Ukrainian president Volodymyr Zelensky.

President Volodymyr Zelensky (right) greets Boris Johnson in Kyiv
President Volodymyr Zelensky greets Boris Johnson in Kyiv (Ukrainian Presidential Press Office/PA)

The timing of the visit led to accusations that he was snubbing the North ahead of a crucial by-election in Wakefield in West Yorkshire, which the Tories are widely expected to lose.

However, speaking to reporters at RAF Brize Norton on his return, Mr Johnson said it was important to demonstrate the UK’s support at a time when the Ukrainians were “suffering terribly” in the face of the ongoing Russian offensive in the Donbas.

“I think it is very important to go to Ukraine at a particularly critical time. The worry that we have is that a bit of Ukraine-fatigue is starting to set in around the world,” he said.

“It is very important to show that we are with them for the long haul and we are giving them that strategic resilience that they need.”

In his talks with Mr Zelensky, Mr Johnson said Britain would be prepared to train tens of thousands of Ukrainian troops as they continue to fight back against the Russians.

Mr Johnson said that it was important to prevent the Russians “freezing” the conflict so they could consolidate their gains before mounting another attack.

He said the Ukrainians should be supported in their ambition to regain territory occupied by the Russian forces since they invaded in February.

However, he stopped short of calling for the recovery of all the lands Ukraine had lost since 2014 – including Crimea – something Foreign Secretary Liz Truss has previously called for.

“It would a catastrophe if Putin won,” Mr Johnson said.

“He’d love nothing more than to say ‘Let’s freeze this conflict, let’s have a ceasefire like we had back in 2014’.

“For him, that would be a tremendous victory. You’d have a situation in which Putin was able to consolidate his gains and then to launch another attack.

“We’ve got to make it clear that we are supporting the Ukrainians in their ambitions … to expel the Russians, expel Putin’s armies, from everything that he has obtained since February 24, and make sure the Ukrainians are not encouraged to go for a bad peace, something that simply wouldn’t endure.”

Mr Johnson’s visit was warmly welcomed by the Ukrainians, with television footage of Mr Zelensky showing the Prime Minister the wreckage of burned out Russian tanks and other vehicles on display in Kyiv’s St Michael’s Square.

Crowds were also shown cheering the two leaders in a video which the Prime Minister shared on Twitter.

The video shows him alongside Mr Zelensky visiting a memorial wall for fallen Ukrainian soldiers, and Mr Johnson praised their “sacrifice, unconquerable courage and bravery”.

He said: “Thank you my friend President Zelensky for hosting me in Ukraine yesterday.

“It was incredibly moving to walk the streets of Kyiv with you once more, to pay tribute to your fallen soldiers whose sacrifice, unconquerable courage and bravery we will never forget.”

The Prime Minister also shared an image of himself and Mr Zelensky speaking around a table, and lighting candles in a place of worship.