Reform UK has reported Green Party leader Zack Polanski to police after he shared an Instagram post containing an image of a man wearing a T-shirt featuring the word “Nigel” above a picture of a guillotine.

The complaint comes just weeks after the murder of former Reform UK MP Ann Widdecombe reignited concerns over the safety of politicians, with Reform figures arguing the image amounted to an unacceptable reference to violence against party leader Nigel Farage.

Polanski briefly shared the post with his more than 700,000 Instagram followers after accepting a collaboration request containing multiple photographs from a Green Party event.

One of the images showed a man wearing a black T-shirt emblazoned with the slogan “We’re only making plans for Nigel” alongside a large illustration of a guillotine.

The phrase is a reference to the 1979 XTC song of the same name, but Reform UK argues the image goes far beyond satire in the current political climate.

Nigel Farage shared a screenshot of the post on X, writing: “If I was to post anything as inciteful then I would expect to be arrested, and so should Polanski.”

Reform UK’s Home Affairs spokesman, Zia Yusuf, confirmed the party had formally reported the matter to police and would also make a complaint to the Greater London Authority’s monitoring officer, as Polanski serves as a London Assembly member.

Yusuf said: “To do this just two weeks after our friend Ann was murdered is staggering.

“This is incitement to murder. It should be treated as such by the police.”

The Metropolitan Police confirmed officers had received a third-party complaint and that enquiries are now under way.

In a statement posted on X, the force said: “We received a third-party report relating to an image shared on social media.

“We take reports of this nature extremely seriously, and officers are conducting enquiries into the matter.”

The Green Party said Polanski removed the post as soon as the image was brought to his attention and insisted he had not realised it formed part of the wider collection of photographs when accepting the collaboration request.

A party spokesperson said: “Once this image was brought to Zack’s attention he immediately unshared the post.

“He unequivocally does not support this type of dangerous message.”

The spokesperson added that Polanski had accepted a collaboration request containing around 20 photographs without noticing the image in question.

“Zack condemns the image on the T-shirt,” the statement continued.

“The T-shirt is clearly in poor taste, especially at a time of heightened fears for the security of public figures, having experienced multiple threats himself.

“He and the Green Party call on everyone involved in public discourse to show kindness and not encourage more division.”

The BBC understands Polanski has not been contacted by police.

The freelance photographer who took the picture also accepted responsibility for the image after the controversy emerged.

Posting on X under the username “just.barold”, the photographer apologised directly to Polanski and said they had reported themselves to police.

They wrote: “This wasn’t intended to offend anyone and it’s clearly not intended as a serious threat to anyone’s safety whatsoever.”

The photographer added that criticism should be directed at them rather than Polanski, arguing the political row amounted to “performative outrage”.

The incident comes during heightened concern over the safety of elected representatives following the killing of Ann Widdecombe earlier this month.

The former Conservative minister and Reform UK MP was found dead at her home in Devon on July 9. A 28-year-old man has since been charged with her murder.

Her death renewed calls for stronger protection for politicians and came in the same year as the anniversaries of the murders of Labour MP Jo Cox and Conservative MP Sir David Amess.

Following Widdecombe’s death, Polanski himself called for increased security for politicians across all parties.

Speaking to BBC Breakfast at the time, he said: “I am worried and I have been worried for a long time.

“I would encourage the government to provide me with extra security, but that is a choice for them.”

Greater Manchester Mayor Andy Burnham has also backed a review of security arrangements for MPs and other elected representatives.

Separately, Reform UK Treasury spokesman Robert Jenrick recently accused the Government of failing to adequately protect Nigel Farage after reports emerged that the party had declined an offer of publicly funded security last year.

The Home Office rejected those claims, stating that decisions on MPs’ security are made by independent security specialists rather than ministers.

The Metropolitan Police has not confirmed whether any criminal offences have been identified. Officers say enquiries remain ongoing while they assess the complaint and the circumstances surrounding the social media post.