The UK government could approve a second Scottish independence referendum if support for staging one stays above 60% for a sustained period, Alister Jack, the Scotland secretary, has said. Jack said consistent support for a fresh vote would confirm to the government that one was justified, as he signalled a further softening of the Conservatives’ previously rigid rejection of Scottish National party demands for a second referendum. “If you consistently saw 60% of the population wanting a referendum – not wanting independence but wanting a referendum – and that was sustained over a reasonably long period, then I would acknowledge that there was a desire for a referendum,” he told Politico.Patrick Harvie, the Scottish Green party co-leader, who is expected to become a Scottish government minister next week if a new cooperation deal with the SNP is supported on Saturday by his party’s membership, said he welcomed the acknowledgment by the Tories that a referendum was a legitimate aspiration. He said Holyrood already had a mandate to stage a new vote, after pro-independence parties won a majority in May’s election, and that opinion poll thresholds were therefore irrelevant. “We have a very clearly pro-independence parliament and I would like to see that parliament debate a bill to set that referendum, and I would like to see the UK government respect that decision,” he told the Guardian. Boris Johnson has previously refused to countenance a fresh referendum despite record levels of support for independence during the Covid crisis last year. The support dropped markedly after the UK vaccination programme began. But facing consistently high polling support for the SNP, senior ministers have slowly diluted that line, to shift the debate away from a battle over Scotland being denied its democratic right to one over the political and economic case for independence. In early August, Michael Gove, the minister in charge of the Cabinet Office and the UK government’s union strategy, told the Sunday Mail: “If it is the case that there is clearly a settled will in favour of a referendum, then one will occur.” The Scottish government is expected within weeks to again press hard for the right to stage a vote, after Nicola Sturgeon, the first minister, agreed the cooperation deal at Holyrood with the pro-independence Scottish Greens.That deal formalises a pro-independence majority of MSPs in Holyrood and pledges to hold a referendum within the next five years. Sturgeon has indicated she wants one held by 2024. Sturgeon is expected to set out referendum proposals when she unveils her government’s new legislative plans at Holyrood on 7 September, before she addresses her party’s annual conference several days later. Jack echoed Gove’s assertion that Scottish voters did not want a referendum in the near future. Support for independence has slipped to well below 50% in a large majority of recent polls. “That’s not where we are and it’s not how I perceive things to be,” Jack told Politico. “I think I’m broadly where the public are, which is that now is not the time to be having a referendum. We’ve had one, we’ve made our decision, let’s get on and rebuild the economy and rebuild people’s lives.”Some polls show a majority of voters forecast that Scotland will probably be independent in the medium-term future, regardless of which way they would vote on it. Jack said he was 100% confident Scotland would remain in the union. “The case [for the union] has made itself,” he said, with the UK’s ambitious vaccinations programme and the billions in Treasury funding for Scotland during the pandemic. The UK government plans to announce billions more in infrastructure and other spending in the coming months. Jack defended Johnson over the prime minister’s “unbelievably crass” remarks about the climate benefits of Margaret Thatcher’s decision to close down coalmines, made on a visit to Scotland in early August. Johnson was trying to be ironic, he said. “He was making light of it. He wasn’t intending to offend anyone, far from it. [All] of us have cracked jokes – they don’t always land the way we expect them to land. We’re all human, but he meant no malice by it … He’s not in the wind-up business.”