Green Party leader Zack Polanski is at the centre of an internal party row after reposting an Instagram carousel that contained an offending image, dragging the party's social media vetting processes into the open and drawing a police complaint from Reform UK.

The post in question was a carousel of 20 images shared to Polanski's 713,000 Instagram followers. Polanski appeared as a co-author on the post because he had accepted a collaborator tag from the original poster. He said he had not noticed the offending image among the others and had accepted collaborator tags for eight other posts from the same event in Bristol. He described the incident as an "inadvertent mistake" (BBC News).

Reform UK leader Nigel Farage said the image — which featured a T-shirt depicting a guillotine — amounted to incitement to murder, and his party reported it to the police (BBC News). Reform UK MP Robert Jenrick called Polanski a "nasty piece of work" at a news conference on Thursday (BBC News).

Neither the Metropolitan Police nor Avon and Somerset Police said the incident met the threshold for further action (BBC News).

The external row has been matched by internal frustration. The Guardian reported on 29 July that Green Party members want Polanski to hand over control of his social media accounts (The Guardian). A senior Green Party source told BBC News that due diligence had not been done on Polanski's social media output and that he needs "tight controls" moving forward to stay credible. The same source said the speed and number of Polanski's social media interactions had a "small upside" but a "colossal downside" (BBC News).

Green Party insiders raised concerns about a wider problem with the party's vetting on social media and of candidates, including around antisemitic posts in recent months. Several Green Party candidates in recent elections stood down over their social media activity; two were arrested during May's local elections; another was suspended after being elected (BBC News).

Not everyone in the party agrees that Polanski's online habits are a liability. Green Party peer Baroness Jones said criticism of Polanski's Instagram repost seemed to be "mainly from our opponents, not internal discussions" and that Polanski "made a mistake". She said his online presence "is what makes him relatable" (BBC News).

The stakes around Polanski's social media conduct are sharpened by his standing on the platform. He is the second-most followed UK political leader on Instagram after Nigel Farage. The Green Party surpassed other parties to become the most popular UK political party on Instagram this year, and according to YouGov it is the most popular party among under-30s in the UK (BBC News).

The party's social media footprint has been a key asset as it builds support among younger voters. But recent polling suggests the Greens have lost ground to Labour following Andy Burnham's election as Labour leader, down from a peak earlier this year (BBC News).

Polanski led the Green Party to its first Westminster by-election victory, in Gorton and Denton, in September 2025 (BBC News). In May 2026 he admitted he was wrong to claim he was a Red Cross volunteer, telling the BBC he had hosted fundraisers for the charity but had not used the right word to describe his role (BBC News). Earlier in July he called for the government to provide him with extra security, saying he was worried (BBC News). He also had to apologise to police last month after posting about their response to the Golders Green attack (BBC News).

The pattern is awkward for a party whose brand is built partly on transparency and digital fluency. Polanski's relatability, as Baroness Jones frames it, is inseparable from the volume and spontaneity that a senior party source now describes as carrying a "colossal downside". The tension between those two assessments is not just about one repost; it is about whether a party that has invested heavily in social media as an organising tool has the infrastructure to manage the risks that come with it.

The wider candidate vetting concerns sharpen that question. If multiple candidates have stood down over social media activity, two were arrested during local elections, and one was suspended after being elected, the issue extends well beyond the leader's account. A party source's admission that due diligence was not done suggests the Greens have been scaling faster than their compliance operation can support.

For political professionals watching from outside, the dynamic is familiar. A leader's personal social media presence becomes both the party's most effective communication channel and its most unpredictable vulnerability. The Green Party now faces the task that every party with a charismatic, digitally native leader eventually confronts: how to impose institutional discipline without suffocating the authenticity that made the leader effective in the first place. That Polanski is the second-most followed UK political leader on Instagram, behind only Farage, makes the calculation unusually consequential.

The police declining to take further action closes the immediate legal question. The political question — whether the party tightens controls, and whether Polanski accepts them — remains open.