Rishi Sunak is under pressure from Conservative MPs to “kick off” a controversial rightwing politician from the party’s approved candidates’ list after his grassroots organisation campaigned to deselect Tory MPs and attacked the integrity of the privileges committee inquiry into Boris Johnson. David Campbell Bannerman, a former deputy leader of the UK Independence party (Ukip) who defected back to the Tories in 2011, has said he wants to stand for the safe South Norfolk constituency, where the party had a majority of just over 21,000 at the last general election. The former MEP launched the Conservative Democratic Organisation last year, alongside the Tory peer and Johnson loyalist Peter Cruddas, to campaign for members’ rights, although the rightwing group also lobbied to have Johnson reinstated as prime minister. The CDO was criticised by the Commons privileges committee after it orchestrated a mass email campaign through its online magazine, to put pressure on the Tory members to step back from the investigation, which concluded Johnson had lied to parliament over the Partygate scandal, leading him to quit as an MP. The group, which was established shortly after Sunak became Tory leader, is also accused of being behind bids to deselect sitting MPs, to wreak revenge on those who helped depose Johnson. Campbell Bannerman has argued that the CDO has simply empowered local members to have a greater say in candidate selections. Nevertheless, angry Conservative MPs said that Sunak, who promised his government would be one of “integrity, professionalism and accountability” when he took over at No 10, should block Campbell Bannerman’s candidacy because of his actions. One said: “Rishi has constantly said that standards and integrity are a part of governing and it remains unclear why, in his capacity as Conservative leader, he’d allow somebody like David Campbell Bannerman on the candidates’ list given his abusive comments about a parliamentary committee. “How can the party square the prime minister’s comments about standards with allowing somebody of that ilk into the party fold?” Another described Campbell Bannerman’s inclusion on the candidates’ list as “insane”. They said: “I don’t understand why central office has allowed him on the list. He doesn’t support the Conservatives; he’s a Ukipper who sought to get Tory MPs deselected. “This would be a bad thing for the party and the prime minister. They just need to kick him off. Nobody gets anywhere near a seat if central office doesn’t want them there. It’s bananas.” The four Tory MPs on the privileges committee received 600 emails from CDO members urging them to reject what they described as a “deeply flawed, biased, and unfair” inquiry. The message, based on a template, accused them of a “politically motivated attack” against Johnson. The email added: “We have witnessed collusion within the civil service and now within the Conservative parliamentary party and the office of the prime minister to reputationally smear and impugn Boris Johnson.” A senior Conservative source said there was currently a “deferment”, meaning Bannerman was not eligible to apply for seats. He has been approached for comment. Campbell Bannerman said: “To seek to defer a comprehensive pass, which would allow me to apply to any seat, on the basis of political considerations – namely a request for me to be nicer about Rishi Sunak on Twitter – is unconstitutional and the legal advice I have received shows that central office are on very shaky ground indeed.” The Tory MP Richard Bacon announced in May that he was standing down from the South Norfolk seat at the next election. Claire Bullivant, the chief executive of the CDO and editor of the Conservative Post, said: “David Campbell Bannerman has nothing to do with the Conservative Post and wasn’t involved with my privileges committee campaign where I asked readers to email the committee members. “So any MP holding my Conservative Post campaign against him is completely wrong. Anyone who knows DCB knows he would make an exceptional MP.” • This article was amended on 28 July 2023. A previous version said the Conservatives had a majority of 36,000 in the South Norfolk constituency. This has been corrected to “just over 21,000”.