Green Party leader Zack Polanski is in trouble after sharing a post on Instagram that contained an offending image. The mistake has caused a fight within his own party and led Reform UK to complain to the police.

The post was a set of 20 images shared with Polanski's 713,000 Instagram followers. Polanski's name appeared on the post because he accepted a "collaborator" tag — a feature that lets two accounts share the same post. He said he had not noticed the offending image among the others and had accepted similar tags for eight other posts from the same event in Bristol. He called it an "inadvertent mistake" (BBC News).

Reform UK leader Nigel Farage said the image showed a T-shirt with a guillotine on it and amounted to incitement to murder. 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 was serious enough to take further action (BBC News).

The argument is not just coming from rival parties. 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 proper checks had not been done on Polanski's social media posts and that he needs "tight controls" to stay credible. The same source said the speed and number of his social media posts had a "small upside" but a "colossal downside" (BBC News).

Green Party insiders also raised concerns about a wider problem with checking candidates' social media, including 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 problem. Green Party peer Baroness Jones said criticism 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).

Polanski's social media presence matters because of how popular he is on the platform. He is the second-most followed UK political leader on Instagram after Nigel Farage. The Green Party became 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 following has been a key advantage as it tries to win over 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 — a vote to fill a single parliamentary seat between general elections — 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 image is built partly on being open and good at social media. Polanski's relatability, as Baroness Jones puts it, cannot be separated from the speed and spontaneity that a senior party source now calls a "colossal downside". The tension between those two views goes beyond one repost. It is about whether a party that has put a lot of effort into social media has the systems in place to manage the risks that come with it.

The wider concerns about checking candidates 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 proper checks were not done suggests the Greens have been growing faster than their ability to manage it.

For people who work in politics and are watching from outside, this is a familiar situation. A leader's personal social media becomes both the party's best way of reaching people and its biggest source of risk. The Green Party now faces the same task every party with a charismatic, digitally skilled leader eventually faces: how to add rules and checks without losing the authentic voice that made the leader popular in the first place. That Polanski is the second-most followed UK political leader on Instagram, behind only Farage, makes the decision more important.

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.