Vladimir Putin’s conquest of Ukraine may take years, Britain’s deputy prime minister has admitted, as Labour accuses the government of moving too slowly on sanctions.

People who thought the crisis could be resolved in days were “delusory,” according to Dominic Raab, and Nato would need to “show some strategic stamina” in order to force the Russian army to retreat.

As the war in eastern Europe entered its 11th day, Raab said Putin was resorting to “ever more brutal tactics to try and wrest back the initiative” because Moscow’s military campaign had “stuttered.”

“I think the bottom line is none of the major cities have yet fallen,” Raab, who is also the justice secretary, told the BBC’s Sunday Morning programme.

“But I think we ought to be under no doubt that our mission with our allies is to ensure Putin fails in Ukraine, and it’s going to take some time.

“We’re talking about months if not years, and therefore we’ll have to show some strategic stamina because this is not going to be over in days.”

Raab vehemently opposed Ukrainian calls for a no-fly zone. He predicted that it would lead to a “massive escalation” in tensions between the Western Defensive Alliance and Russia.

“That feeds Putin’s narrative,” Raab said. “Putin wants to say that he’s actually in a struggle with the west. He’s not. This is an illegal invasion of a neighbour whose self-determination, democratic and territorial integrity needs to be protected. We do not want to feed Putin’s narrative.”