A photographer with the username just.barold claimed responsibility, external for the photo, which he said was of someone wearing a satirical T-shirt, and apologised to Polanski on X, saying "this is not his fault" and adding he had reported himself to the police.

In a series of posts, the freelance photographer said: "This wasn't intended to offend anyone and it's clearly not intended as a serious threat to anyone's safety whatsoever."

They added: "This performative outrage is just that, and if people want to come and take it out on someone then take it out on the person who took the picture, and who then posted it."

However, Reform's home affairs spokesperson Zia Yusuf said the image showed "a photo of man calling for the beheading of Nigel Farage", which he claimed could be an "incitement to murder".

Yusuf confirmed Reform UK had reported the post to police and will also report Polanski to to the monitoring officer at the Greater London Assembly, where the Green leader is an elected member.

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

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

Prominent Reform member Widdecombe, 78, was found dead in her home in Haytor, Devon, on 9 July. A man, 28, has been charged with her murder.

Her death reignited a row about the security of political figures in public life, with this year marking the 10th anniversary of the murder of Labour MP Jo Cox and the fifth anniversary of the murder of Conservative MP David Amess.

Following Widdecombe's death, Polanski called for all party leaders to get extra security.

Asked about Widdecombe's death at the time, he told BBC Breakfast: "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."

Andy Burnham also backed a serious review of MPs' security earlier this month.

Reform UK's Treasury spokesman Robert Jenrick had accused the government of a "dereliction of duty" over Farage's security, after it emerged the party turned down a government-funded security offer last year.

The Home Office said Jenrick's comments were "categorically untrue", and that independent security experts, not ministers, held responsibility for deciding MPs' security.