British police are investigating an image featuring a guillotine and a reference to Reform UK leader Nigel Farage after it was reposted on social media by Green Party leader Zack Polanski.

Reform UK confirmed that it had reported the post to police. Senior party figure Zia Yusuf described the image as “incitement to murder.”

The complaint came slightly more than two weeks after former MP and party spokesperson Ann Widdecombe was found dead at her home on July 9 after being struck 21 times with a hammer. A 28-year-old man has been charged with her murder.

The image shows a man making a victory sign while wearing a shirt depicting a guillotine alongside the phrase “We’re only making plans for Nigel,” a reference to a song released by British rock band XTC in 1979.

The Green Party said Polanski condemned the image and had approved a multi-image social media post without realising it contained additional photographs beyond those he had initially viewed.

An independent photographer originally published the image as part of a collection from an event attended by Polanski in Bristol on Sunday. The post was edited on Monday to remove the photograph, while police confirmed that an investigation was underway.