Mr Polanski, who last weekend revealed he has never taken illicit substances, denounced the jibes as “disgraceful” and accused the Prime Minister of deploying “cheap jokes” on serious issues.

However, Labour has also been taking aim at Mr Polanski on social media, with the party’s official social media account sharing the Green Party leader’s “top five cringe moments” during his stint as a Liberal Democrat member.

Meanwhile, Labour joined Reform UK in heaping pressure on Mr Polanski, with Zia Yusuf sending an excoriating open letter to the Green Party leader inviting him to a head-to-head debate last weekend.

Reform UK’s policy chief included attacks against Mr Polanski on his support for legalising hard drugs, pulling out of Nato and supporting “a world without borders”.

“Voters deserve to know what they’d get with Zack Polanski and his nonsense party,” a Reform source told GB News.

Sir Keir Starmer is facing his biggest test as Prime Minister

“That’s why he’s ducking the debate. He knows his open-borders, tax-the-rich agenda won’t win over voters who want real change – and only Reform UK is offering it.”

Mr Polanski rejected Mr Yusuf’s request, instead opting to challenge Mr Farage to a debate.

However, Mr Farage quickly shut down the suggestion, telling journalists: “If you pick a fight with a chimney sweep you get covered in soot.”

Despite being accused of parroting simple solutions to huge problems, Mr Polanski continues to pose a huge threat to Labour.

There is no love lost between Labour and the Green Party, with both looking to cement the position of Reform’s main rival in Gorton & Denton.

However, veteran Labour campaigners have warned Sir Keir needs to be careful about giving Mr Polanski exposure which could see more voters switch to the Green Party.

Labour launched attacks against Nigel Farage and Matthew Goodwin

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“I assume the tactic is to paint him as silly and hopeless to encourage people to stick with them rather than him,” one told GB News.

“Sadly, I think for lots it’s too late for all that but the brains trust at HQ will think it’s wise, I’m sure.”

Another veteran campaigner said: “I really don’t understand this strategy at all.

“Not only does this strategy actually elevate Polanski, but I’ve seen over and over again that these posts on Instagram are riddled with negative responses from people.

“They say that these types of posts are pushing them closer to the Greens because they find the content unsavoury.

“People are sharing that they’re uncomfortable seeing Labour attack a party that many would like to see Labour collaborate more with.

Green Party leader Zack Polanski is now seen as a huge threat to the Labour Party

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“I haven’t seen any evidence in the comments or how people are responding to this digital content that the strategy is working.”

Despite some Labour voters seeing Mr Polanski as a collaborative figure, the Green Party leader has refused to work with Sir Keir to block Mr Farage’s march to power.

However, the Labour strategist suggested Sir Keir should go further in his attacks against Mr Farage, focusing on Russia, the NHS and workers’ rights.

However, the Prime Minister was also urged to lay out a positive and proactive message of what Labour is looking to achieve, which Sir Keir attempted to explain during his “Pride of Place” event in Hastings.

“The reason people are drawn more to the Greens and Reform alike is that they have a bold take on where they want to see the country,” they added.

“Labour instead spends too much of its time finger-pointing, assigning blame to the Tories, or infighting to maintain control.

“They’re not delivering a bold vision for the future, and they certainly aren’t communicating it online effectively.”

Sir Keir Starmer has ordered an ‘urgent’ investigation into Lord Mandelson’s Labour peerage | GETTY

It would appear that the Prime Minister has taken heed of the advice following a backlash from Labour MPs over Lord Mandelson.

Labour’s official TikTok account has not taken aim at Mr Polanski since Wednesday, instead releasing three videos blasting Reform UK.

It is a similar story on X, with Labour targeting Mr Farage and Reform UK’s Gorton & Denton by-election candidate Matthew Goodwin.

However, polling conducted by YouGov suggests Labour is only holding onto 38 per cent of its vote from 2024, with 15 per cent going to Labour, nine per cent going to the Liberal Democrats and eight per cent shifting to Reform UK.

The same pollster this week revealed that 50 per cent of Britons want Sir Keir to resign as Prime Minister, including 37 per cent of Labour voters and 44 per cent of Green voters.

“I think it has little chance of backfiring on Reform as there is relatively little overlap between Reform and Green voters,” Merlin Strategy pollster Scarlett Maguire told GB News earlier this week.

Zack Polanski is setting his sights on the Gorton & Denton by-election

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“However, Labour attacking Polanski does have some risks because, at the moment, he’s more popular than they are.”

Gorton & Denton is expected to be a major test for Labour, with insiders fearing a Caerphilly-style disaster if the Green Party emerges as the main challenger to Reform UK by polling day.

Such a scenario risks jeopardising Labour’s campaign message ahead of the 2029 General Election.

It could also leave all anti-Reform parties battling it out to show progressive voters that they are the best bet to halt Mr Farage’s march to No10.

GB News has approached the Labour Party for comment.