Reform UK has ditched five candidates in the past week over racist, homophobic and obscene posts unearthed on social media, including one prospective MP who said that Africans had IQs “among the lowest in the world”.

The party is neck and neck with the Conservatives in the north and Midlands, according to recent polling. Nigel Farage, the former Ukip leader, has hinted at a political comeback and the party was buoyed by the recent defection of Lee Anderson, the former Tory party vice-chairman.

But in the past week alone five prospective parliamentary candidates, Jonathan Kay, Mick Greenhough, Pete Addis, Amodio Amato and Ian Harris, have been dropped because of social media posts.

Addis, the candidate in South Shropshire, was removed after The Mail on Sunday discovered a string of racist, sexist and homophobic posts.

He used a derogatory word for a Chinese person on Facebook and described Angela Rayner as a “slag” and also wrote: “Bum sex, this is where brown babies come from!” Addis said of the Chinese slur: “There was nothing meant by it, it was because we had a lot of … Chinese food, when we were growing up. That wasn’t intended to be racist, it was something my mum tagged me in to.”

Amato, the candidate in Stevenage, described London as an “Islamic State” and said there would be “a Muslim army run by Sadiq Khan”.

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In an effort to tighten up its campaign, Reform UK is trying to improve the vetting of candidates. Candidates for Ukip and the Brexit party, forerunners to Reform UK, were regularly discovered to have posted obscene comments on social media.

Hope Not Hate, a charity that campaigns against the far right, also exposed messages by Kay, Greenhough and Harris, all of whom have now been dropped.

Kay, the candidate for South Ribble, said that Africans had IQs “among the lowest in the world” and Muslims “never coexist with others”.

Greenhough, the candidate for Orpington, said in 2019 that Ashkenazi Jews were a “problem” and had “caused the world massive misery”. Last year he said that “the only solution” was to “remove the Muslims from our territory”.

Harris, the candidate for Lewes, liked a tweet by Nick Griffin, the former leader of the British National Party, which described the UK as a “bankrupt, crime-ridden, LGBTQ-obsessed, multicult shit-hole” and another tweet by Tommy Robinson that called for “mass deportations”.

Richard Tice, leader of Reform UK, has promised to put up candidates in every constituency, something that pollsters believe could seriously harm Tory chances at the election.

Reform UK is only four points behind the Conservatives, according to the latest YouGov poll for The Times. It has climbed to 16 per cent compared with 20 per cent for the Tories. But a YouGov MRP poll suggested that it was unlikely to return any MPs because its votes were not concentrated.

A spokesman for Reform UK said the party had “hundreds” of people applying to be candidates and promised more vetting. “The party will not be represented by racists, sexists and homophobes,” he said.