Someone who would vote against equal marriage should not be first minister of Scotland, and could not be trusted to fight subsequent attempts to roll back rights, the SNP leadership candidate Humza Yousaf has said. His closest rival, Kate Forbes, caused an outcry last week when she revealed she would not have supported the Scottish government’s equal marriage legislation had she been an MSP at the time, and one of the party’s most prominent LGBTQ+ politicians this weekend said scrutiny of such views should not be dismissed as “abuse”. Yousaf has been asked about Forbes’ views previously but hardened his position on Sunday. Pressed by the BBC’s Laura Kuenssberg about whether it would be acceptable for the first minister of Scotland to be someone who did not agree with equal marriage, he replied: “Not if they would roll back on those rights, I don’t think that’s acceptable.” “If they were able to disassociate their view, and not let that interfere with policymaking or legislating, then I think that’s a different matter. “But if they have already said that they would roll back or vote against those rights, then what would happen, for example, if somebody brought in a member’s bill or a piece of legislation to try to roll back on equal marriage?” Yousaf was endorsed on Sunday by the prominent MP Mhairi Black, after she issued a strongly worded statement describing the “hurt” caused to her personally by Forbes remarks and asking “how I, and others, are expected to have faith in a leader who unashamedly and publicly believes the love between my wife and I should not be legally recognised?” Black cautioned against describing the response to Forbes as a “witch-hunt”. She said: “Holding candidates to account, and scrutinising what they have said themselves – on camera, voluntarily, as a pitch to be the next FM of Scotland – is not abuse.” Forbes, a member of the socially conservative Free Church of Scotland, lost the backing of leading supporters when she spoke candidly about her faith-based views in a series of interviews to launch her leadership bid. She said she would not challenge the UK government’s block on gender recognition reform and that her faith told her having children outside of marriage was “wrong” and was something she would personally “seek to avoid”. Despite this, polling for the Sunday Times shows that Forbes leads Yousaf as the favoured successor among SNP voters by a narrow margin of two points. Forbes polled 20%, with Yousaf on 18% and the third candidate, Ash Regan, a former junior minister who quit the government to protest against the government’s gender recognition reforms, on 9%. Only SNP members can vote in the ballot, which closes at noon on 27 March, with the result expected to be declared that day. On Saturday, the Scottish Association of Mosques intervened in the leadership race in what appeared to be a coded snub to Yousaf, stating it would not endorse any candidate but adding: “It is refreshing to hear a political leader talk about their religious values and principles in an open and transparent way.” Asked about this intervention by Kuenssberg, Yousaf, who is a practising Muslim, said: “I do not use my faith as a basis for legislating”, adding that policymakers “have to look at what we think is in the best interest of society as a whole”. He was also questioned about the allegation made by the former minister Alex Neil, who led the legislation on equal marriage in 2014 and is supporting Forbes, that he had missed the final vote on the bill because he was under pressure from Muslim leaders. Yousaf noted that Neil was “backing another candidate”, adding “the fact that this issue has been dragged up nine years old and in the midst of a leadership campaign probably tells you the motivation behind it”. He restated he voted for the bill earlier in the process and that at stage three had an “unavoidable meeting” with the Pakistani government regarding a Scot on death row, who was later released. On Sunday, Forbes gave a series of interviews in which she promised £800m to tackle the cost of living crisis, warned that transitioning from oil and gas “too quickly will only damage the Scottish economy” and promised to pause the controversial Scottish Greens-fronted deposit return scheme. She also confirmed to the Scottish Mail on Sunday that she was the author of a blog that described the ordination of women as “a great injustice” and against God’s plan.