The Scottish Greens would demand far tougher climate policies in exchange for agreeing to a coalition deal with the Scottish National party after the May election. Senior SNP strategists have mooted offering a coalition deal to the Greens as a way of forming a pro-independence “super majority” at Holyrood for the first time since the party won power 14 years ago. That follows a sustained dip in SNP support in some recent opinion polls, which has dented expectations Nicola Sturgeon will easily win an overall majority at Holyrood on 6 May. If she fails to win that majority, a formal government deal with the Greens would allow Sturgeon to argue Holyrood had a mandate to demand a second referendum. The Greens have five MSPs and expect to win several more seats in May. Patrick Harvie, co-leader of the Scottish Greens, told the National newspaper earlier this month he was open to the idea of a formal power-sharing deal, but a Greens spokesman said there had not yet been any contact on that between the two parties. Any formal deal would be a “non-starter”, he added, unless Sturgeon cancelled the Scottish government’s road-building plans, which include dualling long trunk roads, and dropped support for taxpayer subsidies for North Sea oil and gas extraction and exploration. “If any party wanted to speak to us they’d have to get serious on the climate emergency. They would have to seriously shift on climate if they were to give us any ministerial posts,” the spokesman said. Any offer would need to be ratified first by party members, he said. SNP politicians and members could resist a deal that tied the party’s hands: despite running minority governments twice since 2007, the SNP has never entered into formal coalitions. SNP strategists argue that a coalition government with the Greens could bolster the Scottish government’s credentials before Glasgow hosts the Cop26 global climate talks in November. Sturgeon’s climate policies have come under repeated attack from the Greens for being far too timid. Sturgeon has shifted away from calling for an early independence referendum after the same polls found falling support, and opposition parties accused her of prioritising constitutional conflict above Covid recovery and domestic policies. The yes vote hit a record high of 58% at the peak of the Covid pandemic, with more than 20 polls in a row giving independence a majority, as voters endorsed Sturgeon’s leadership during the crisis. But with the success of the UK government’s vaccinations strategy, and the Alex Salmond harassment crisis, it has since dropped. The elections expert Sir John Curtice said the last six polls put yes and no support at 50/50; for the first time in a year, some show a clear lead for no. Others show a minority of voters favour a quick referendum. Sturgeon’s recent shift towards prioritising the Covid recovery, and suggestions the SNP would delay a referendum for at least two years, has put Scottish Labour under pressure to offer a clear alternative to the SNP at the election. Anas Sarwar, the new Scottish Labour leader, told reporters on Thursday, as he launched Labour’s campaign, he believed Sturgeon’s pledge to put Covid first was insincere. “Whilst the Tories and SNP can talk about recovery, they’re both compromised. The Tories can’t deliver a recovery that works for everyone because they would have us go back to the failed system and inbuilt inequalities we had pre-Covid,” he said. “The SNP will try and talk about recovery, but it’s not credible to say we’re going to come through Covid and straight into a referendum campaign which is going to pull our country further apart.” Douglas Ross, the Scottish Tory leader, said denying the SNP a majority on 6 May would stop their quest for a second referendum. “We know from the referendum bill they introduced on Monday that is going to be their top priority, should they be re-elected as a majority. And therefore we have to stop that at all costs,” he said.