One of the SNP leadership’s fiercest critics has called on the party to change course and ditch its “dreadful” governing partnership with the Scottish Greens, as he lost his appeal against a week-long suspension from the Holyrood group. Fergus Ewing, one of the party’s longest-serving MSPs, a former minister and son of the SNP icon Winnie Ewing, faced disciplinary action after he voted against the government on a no-confidence motion against the Green minister Lorna Slater brought by the Scottish Tories, prompted by her handling of the deposit return scheme. The SNP’s Holyrood group voted to take action against the Inverness and Nairn MSP last September by 48 votes to nine with four abstentions but Ewing appealed, arguing that this was a conscience vote and that he was representing his constituents’ concerns about the “abject failure” of the scheme. His appeal failed and on Tuesday his suspension – the first sanction of its kind used by the SNP at Holyrood – was confirmed. Ewing immediately released a statement describing the SNP as “authoritarian”, with a leadership that “no longer tolerates a conscience vote”. Speaking on BBC Radio Scotland on Wednesday morning, Ewing called for the party to “go back to the middle ground, to be a broad church representing everybody in Scotland, accepting that people can have different views, social conservatives as well as progressives”. He said: “I want a tolerant Scotland where we can all work together for the good of the common weal. And I think that the SNP is still the main vehicle to achieve that and to take us towards independence. That will only happen if we pursue a different path and get rid of the dreadful deal with the extremist Greens.” Ewing has been a regular critic of the Bute House agreement, which was brokered by the former SNP leader Nicola Sturgeon after the 2021 Holyrood election, giving voice to growing disquiet within the Holyrood group and the wider party about the influence of the Greens on policymaking and electoral appeal. He has also criticised Green-led Scottish government policies on gender recognition reform and highly protected marine areas and regularly challenged the leadership on delays to widening Highland roads. While Ewing may be the most outspoken critic of the current leadership, he is supported by other significant figures including Kate Forbes, who was narrowly beaten by Humza Yousaf to the party leadership last year. Her supporters have previously told the Guardian that Yousaf may face a leadership challenge if SNP losses at the general election reach a tipping point. Ewing said the membership of the SNP should be allowed to vote on the Bute House agreement “now that we’ve had the experience of two and a half years of dismal mismanagement and duff policies from the Green party, which have only served to bring the SNP down in terms of votes and trust”. He said he had voted against Slater because that represented the views of “hundreds” of businesses he had spoken to who did not feel that the policy was being handled competently. “If my constituents wanted a doormat, they would have gone to B&Q,” he said. At a press conference on Wednesday morning, Yousaf denied Ewing’s suggestion that his party was authoritarian, as he published analysis estimating that 100,000 children will be kept out of relative poverty in 2024-25 as a result of Scottish government policies. Yousaf said tackling poverty remains the “driving mission” of his government, despite ferocious criticism from homelessness and child poverty groups of the Holyrood budget passed by MSPs on Tuesday. He said he understood charities’ frustrations but hoped that they appreciated the constraints on his budget, and he suggested charities should apply pressure on the incoming UK government. “We will continue to take the actions as necessary within the powers that we have, but I would say to those charities … to equally exert pressure on the current and the incoming UK government to make the changes necessary to lift children out of poverty,” he said. He suggested that a new Labour government could “at the drop of a hat” decide to scrap the two-child limit and introduce an essentials guarantee to reform universal credit provision. Responding to the analysis, John Dickie, the director of the Child Poverty Action Group (CPAG) in Scotland, said the projection made clear that the government’s policy package was insufficient to reach its own legally binding target of less than one in 10 children living in poverty by 2030.