Rishi Sunak is facing a further test of his leadership as another ally of Boris Johnson quit parliament, triggering a third byelection. Nigel Adams, who had already confirmed his plans to retire at the next general election, on Saturday afternoon decided to stand down with immediate effect. The former minister was nominated by Johnson for a peerage, but did not make the final list alongside Nadine Dorries, Sir Alok Sharma and Alister Jack. Sunak had blocked Johnson’s allies on the peerages list to avoid difficult byelections, which appear to be trickling in regardless. Announcing his resignation, less than 24 hours after Dorries and Johnson, Adams said on Twitter: “Yesterday, Selby Conservatives selected an excellent new parliamentary candidate. I’ve today informed the chief whip that I will be standing down as a Member of Parliament with immediate effect. “It has been an honour to represent the area where I was raised, educated and I want to thank my constituents for their wonderful support since 2010.” At least five hours before Dorries dramatically announced plans to quit parliament, she told TalkTV that “the last thing I would want to do would be to cause a byelection” in her seat. Soon afterwards, Johnson followed the lead of one of his fiercest allies, with a blistering attack on Sunak’s leadership and the Partygate inquiry. CCHQ has been holding byelection drills for at least a month, the Guardian understands, amid fears Johnson and his allies would quit in order to accept peerages. The drills have consisted of outlining what the priority issues within each seat were, and which ministers should make visits to each constituency and why. All eyes will be on Sharma, the former Cop president and current MP for Reading West, who may also quit in protest, as sources insist more resignations are on the way. Some insiders have suggested the Scotland secretary, Alister Jack, the MP for Dumfries and Galloway, may not be willing to give up the plush cabinet position he has held since 2019 in order to join in the “revenge” against Sunak. The Liberal Democrat deputy leader, Daisy Cooper, said: “The Conservative party is in meltdown and must now call a general election. After years of failing our NHS and failing to deal with the cost of living crisis it is time people across the country have their opportunity to give a verdict on this chaotic Conservative government.” A number of Tory MPs are concerned the party will lose all three byelections, with one claiming the public will not put their faith in Sunak,. “Sunak must learn [from these byelections] that he cannot ignore a third of his party, rip up the 2019 manifesto and hand control of the entire government to Jeremy Hunt,” one said. Another urged the prime minister to “offer something new” before the Tory party conference in October, as simply reshuffling the government before parliamentary recess would not be enough of a “reset”. Adams had successfully defended his Selby and Ainsty constituency three times since 2010, which has been Conservative since its creation that year. Adams, who has held a number of ministerial posts since his election, described the Conservative candidate for his seat, Michael Naughton, as “excellent”. Naughton beat the former Financial Times Whitehall correspondent and author Sebastian Payne, lawyer Zak Khan and councillor Andrew Lee. Labour is widely tipped to win an electoral contest in Uxbridge, a constituency Johnson is thought to have been making a chicken run away from in the hope of securing a much safer seat such as Henley, while the Lib Dems have long been pouring their resources into Mid-Bedfordshire, with activists touring the constituency on Saturday. A source said the party would need a swing of 23.6%, which is much lower than was needed to make the historic byelection wins in Chesham and Amersham, North Shropshire and Tiverton & Honiton. The polling expert Luke Tryl, from More in Common, believes Labour should be able to win in Uxbridge otherwise there is something “seriously off” with polling. In Mid-Bedfordshire, the Lib Dems “should start as the favourites”, but he noted the constituency is filled with “traditional Conservative voters and Cameronite Tories”. “These tests will be a real chance to see if Sunak is saving the day,” he said. Adams’ former constituency of Selby could be the first chance to see if “Labour is on course to win 1997 or somewhere short of that mark”, Tryl said. “Although it’s a solid seat for the Tories on current boundaries, Tony Blair got big swings in byelections in the 1990s from the Tories. Blair won the south Staffordshire byelection in 1996, overturning a 7,000 majority, ahead of his historic election win. An hour before Adams stepped down, the long-serving Conservative MP and staunch Brexiter Bill Cash announced he would step down at the next election and retire from political life. The 83-year-old chair of the Commons’ European Scrutiny Committee and MP for Stone in Staffordshire said it would be a “big wrench” to leave parliament after four decades as an MP. He was first elected in 1984 and re-elected in 2019 with a majority of almost 20,000. In a statement, he paid tribute to his wife, Biddy, for her “continuous advice and support”, and thanked constituents for “their loyalty to me and their common sense”.