Reform UK has suspended one of its key mayoral candidates after he described members of a Jewish neighbourhood watch group as “cosplayers” and likened them to “Islamists on horseback”.

Chris Parry, who had remained the mayoral candidate for Hampshire despite a previous controversy in which he said David Lammy should “go home” to the Caribbean, made the latest comments on Monday about Shomrim, a volunteer group that safeguards communities including Orthodox Jewish families.

The former rear admiral was condemned for comments made when he retweeted a post on X by Catherine Blaiklock, a co-founder of the Brexit party, hours after news emerged of an arson attack on ambulances run by a Jewish charity in London.

“Can Christian’s [sic] in Britain set up their own police and patrol certain neighbourhoods?” said Blaiklock, who posted a picture of a number of Shomrim vehicles.

Parry shared the post, adding: “Remember that these cosplayers have no more jurisdiction or legal authority than ordinary citizens.”

When he was challenged over the original post’s characterisation of Shomrim, Parry replied: “They are a community organisation, not a legal entity. It’s the same with Islamists on horseback.”

When contacted by the Guardian after news that he was being dropped and would be investigated, Parry said that was not what he understood and that he was “mid-Atlantic”.

A Reform UK spokesperson said: “Chris Parry has been suspended by Reform UK pending investigation.” The party has also suspended his mayoral candidacy.

Shomrim has worked alongside Hatzola, the charity ambulance service that was targeted by arsonists early on Monday morning and provides emergency medical response and transportation to hospitals for both Jewish and non-Jewish people.

Shomrim’s president, Rabbi Herschel Gluck, described Parry’s comments on Monday as “ignorant” of the organisation’s work, adding: “It shows a level of bias and ignorance which I’m surprised at given that this is a politician who aspires to be a mayor.”

Parry, who is also the honorary president of Veterans for Reform, a group that brings together ex-military personnel supporting the party, had been set to stand in the Hampshire and the Solent mayoral contest in 2028.

He had apologised for his “clumsily worded” post on X about Lammy in January after saying the deputy prime minister, who was born in London to Guyanese parents, should “go home to the Caribbean” where his “loyalty lies”.

Nigel Farage had expended political capital on defending Parry, describing some of his past comments as “a bit rich” but insisting he was “intensely patriotic” and had given enormous service to the UK.

However, the latest controversy appears to have tipped the Reform UK leader over the edge as he faced being questioned about Parry’s latest comments at a time when Jewish communities are reeling in the wake of the arson attack in Golders Green and Reform is preparing for elections in May.

The party now faces having to find a new candidate to replace Parry for the Hampshire and the Solent mayoralty, a new post created after a new combined authority was agreed by the government and that Reform would have been in a strong position to win.

The Liberal Democrats’ home affairs spokesperson, Max Wilkinson, had called on Farage earlier in the day to drop Parry. He later said: “This is a good start, but Farage has some way to go. There are serious questions to answer as to how this candidate got approved in the first place.”

Calvin Bailey, a Labour MP who wrote to Farage about previous comments attributed to Parry, including calling female MPs “harpies”, said: “It should not take repeated incidents for basic standards of decency to be upheld.”