A Reform UK candidate who called for a “white Britain” and said Keir Starmer should be shot is among a number of contenders fuelling doubts about the party’s claim to have tightened up its vetting.

The past comments of Linda McFarlane and other political hopefuls have been unearthed ahead of the 7 May elections, including one who complained about “constant kowtowing to the black community” and others who endorsed the far-right activist Tommy Robinson.

Labour is preparing to run a party election broadcast on Friday that will seek to expose some of the “toxic” views of Reform figures, warning viewers in advance of offensive language.

While Nigel Farage, the Reform leader, and senior colleagues have insisted the party’s vetting processes are as tough as any other, Reform was under pressure this week over views and positions linked to a fresh batch of candidates identified by the anti-racism campaign group Hope Not Hate.

They included McFarlane, who is Reform’s candidate in the Gateshead ward of Chopwell and Rowlands Gill. A social media account in her name tweeted “you should all be shot” at accounts used by Starmer and the justice secretary, David Lammy.

When would-be Reform candidates were going through vetting, the McFarlane account posted: “These Black people who feel their colour is against them. Maybe it’s because they arent good enough!!!!. These Black people need to get used to the colour of their skin You don’t hear Chinese or other ethnics pull the ‘race card’. Pathetic.”

Of immigrants, the account said, “Let them all drown” and called for a “white Britain” and a parliament with only white MPs. McFarlane was approached for comment.

The party was also challenged over allegations that James Grainger, a county councillor in Devon who is up for re-election, had used a YouTube account to make anti-Muslim and pro-Putin comments.

When Zia Yusuf stepped down as Reform’s chair last year before making a return, the account said: “So happy to see Zia gone. He was a muslim and definitely against the values and direction of reform.”

The account had disclosed a series of details that matched the age, background and occupation of Grainger, including those declared in his register of interests. Grainger has been approached for comment.

A YouTube account in the name of Jason Patchett, Reform’s candidate in Hoveton and the chair of the party’s North Norfolk branch, said in 2022: “Constant kowtowing to the black community is not doing us any favours. It is predominantly that demographic which is causing the issues but we’re frightened to do anything.”

The comment was made on a since-deleted YouTube account, which has been archived by Hope Not Hate. Patchett has been approached for comment.

Joe Mulhall, the director of research at Hope Not Hate, said: “Reform UK’s ‘common sense’ vetting procedure which Zia Yusuf had described as ‘the best’ in the country has proven time and time again to be completely inadequate.

“After the last general election, Nigel Farage pledged that ‘the bad apples’ would be gone from his party. But with Reform continuing to put so many up for election, the only conclusion is that there is a systematic failure with its vetting.”

Reform has been contacted about Grainger and McFarlane as well as a number of other candidates alleged to have made offensive comments.

Labour’s election broadcast will include Farage’s description of the misogynist influencer Andrew Tate as “a very important voice” and Reform MP Sarah Pochin’s comment that “it drives me mad when I see adverts full of Black people”.

Others featured in Labour’s broadcast include Aseem Malhotra, a doctor who addressed Reform’s annual conference and repeated claims that members of the royal family had developed cancer as a result of Covid vaccines.

The communities secretary, Steve Reed, challenged Farage to throw out 45 Reform candidates who Labour said were on the record for making offensive remarks.

Reed said: “The idea that Nigel Farage thinks these candidates pushing vile racism, misogyny and conspiracy theories are suitable, is frankly staggering.”

The candidates highlighted by Labour included Alan Stay, a candidate for Reform in the Isle of Wight who shared racist and sexist messages online, including one that repeatedly used an explicitly racist epithet, arguing that it was not a harmful word.

Another candidate, Caroline Panetta, who is standing in the outer London borough of Bexley, retweeted anti-Islam comments, including one saying Sadiq Khan, the London mayor, wanted to turn the city into “Londonstan” where women would be unsafe.