Labour has branded Zack Polanski “delusional” after the Green Party leader claimed Keir Starmer shared his scepticism about the future of Nato.

Polanski has called for the UK to leave the defence alliance, urged Britain to wean itself off its reliance on the United States and consider expelling American forces from British bases.

Meanwhile prime minister Keir Starmer is trying to hold the alliance together just one month after Nato-sceptic Donald Trump threatened to invade Greenland.

European leaders are also relying on the strength of Nato to deter Vladimir Putin from attacking countries beyond Ukraine, where the alliance’s eastern flank is.

But Polanski told HuffPost UK: “The prime minister has moved much closer to my position [on Nato].

“In fact, the speech he gave in Munich last week could have easily been a speech I gave six months to a year ago.”

Starmer told the Munich security conference that it was time to “build a stronger Europe and a more European Nato” to combat Russian aggression at a time when Trump is turning away from the alliance.

The PM also used the speech to hit out at “the peddlers of easy answers” who who are “soft on Russia, weak on Nato” – an attack on both the Greens and Reform UK.

Polanski said Starmer appeared to be “ridiculing me for my Nato position,” even though he wants to set an alternative alliance which has British security “at the heart”.

“It feels he’s accepting the fundamentals of what I was saying but at the same time still trying to use desperate political attacks rather than actually deal with the substance, which is Trump is unpredictable and dangerous,” he said. “He’s not an ally at this point.”

Polanski continued: “Starmer has realised banging on about the special relationship with a president who is so clearly uninterested in the UK and our security was no longer tenable. So I think he’s moved to the right position.”

A Labour spokesperson rejected these claims, calling the remarks “delusional”.

They said: “Zack Polanski’s claim is delusional and is just further proof that the Greens cannot be trusted with our national security.

“While Putin wages an illegal war in Ukraine, the Green Party wants to take Britain out of Nato and leave our country isolated and exposed.

“Labour will always stand firm with our allies, uphold our commitments to Nato, and defend democracy and the rule of law.”

Polanski also claimed that his previous claims that the UK should negotiate directly with Putin over Russia’s nuclear powers have been “mischaracterised as sitting down and having a friendly chat”.

Insisting that he does care about national security, he said: “Sanctions are a part of diplomatic relationships. I think there’s still more we could be doing around showing global leadership in terms of the rest of Europe.”

“I think there’s still more we could be doing around sanctions,” Polanski said. “Once you’ve exhausted every possible option, then you ask for the further military question too.”

When pressed over whether that meant sending troops to fight in Ukraine, he said: “I don’t have access to all the intel on that.

“I think there’s a principle at stake here that is we should never rush to more war, we should never rush to more weapons, we should never look at saying we’re done with diplomacy, because actually there’s been lots of times in the past where it’s felt like hope has totally been lost with other countries.”