Nicola Sturgeon plans to stage a fresh Scottish independence vote late next year without authority from Boris Johnson’s government, in a move likely to provoke lengthy legal battles. The first minister said on Tuesday she would update Holyrood on her plans “very soon indeed” as she released a report claiming Scotland should aspire to match the prosperity rates of small European countries such as Denmark and Ireland after independence. Sturgeon said she had an electoral mandate to deliver a referendum with or without Westminster’s agreement, and claimed her government had devised a legally secure alternative route to holding one regardless of that approval. The legislation that set up the Scottish parliament stipulates that Westminster has to authorise any referendum affecting the UK constitution, under a so-called section 30 order. The 2014 referendum, which the no side won by 55% to 45%, was called after the then prime minister, David Cameron, agreed to provide a section 30 order because Alex Salmond, the then first minister, had won a landslide Holyrood election victory in 2011. Many constitutional lawyers and pro-UK parties believe that is the only lawful route. The former prime minister Theresa May and Johnson have repeatedly refused to authorise a fresh referendum, saying the 2014 result was definitive. Standing with Patrick Harvie, the Scottish Green party co-leader, alongside her at Bute House, her official residence in Edinburgh, Sturgeon refused to provide any further details about her alternative strategy. But she agreed that it would face obstacles that she declined to specify. “We are dealing with a prime minister that doesn’t respect democracy, the law or any of the norms that underpin democracy in the UK,” she said, alluding to Johnson’s attempts to rewrite the Northern Ireland protocol and his refusal to resign over the Partygate scandal. “I have to deal with that reality. Does that pose challenges? I’ll set those out. And the ability of the Scottish parliament to legislate without a section 30 order is contested. I believe we can navigate a path forward but I’m going to do that responsibly, I’m going to do that properly.” Sturgeon faces the significant prospect that an unorthodox route will be challenged at the UK supreme court. She may propose that the UK and Scottish governments jointly apply to the court for a ruling. That presents the clear risks that Johnson will refuse to do so or that the court will declare her proposals unlawful. The UK government and pro-UK parties could boycott a referendum held without a section 30, undermining its political legitimacy. Sturgeon has put a premium on staging a lawful and legitimate event to ensure it has international approval, particularly within the EU. Rejoining the EU is being presented by Sturgeon as one of the major benefits of independence. The paper published on Tuesday, Independence in the modern world – wealthier, happier, fairer: why not Scotland?, is the first in a series that Sturgeon’s government is publishing over the coming months in an effort to set out a refreshed case for independence and reverse a decline in the yes vote. The document was described as “cherrypicking and jam tomorrow” by opposition parties after it compared the UK’s poor economic performance and higher poverty rates only with the records of 10 high-performing small countries such as Norway, Austria and Belgium. It ignored larger countries or those with weaker economies. Sturgeon refused to say how long it would take for an independent Scotland to regenerate its economy. She said the economic crises were exactly why independence was necessary. “The sooner we get on to that path, the earlier we will work our way towards the kind of success that they [other countries] enjoy,” she said. The Conservatives, Labour and the Liberal Democrats said it was ruinous to pursue an independence referendum in the midst of an economic crisis, with the UK facing a recession, a fresh crisis over Brexit, and so soon after the Covid pandemic. Anas Sarwar, the Scottish Labour leader, said: “You cannot play politics while people’s lives and livelihoods are in the balance.”