JOANNA Cherry has called for Holyrood to hold a second independence referendum without agreement from Boris Johnson should he continue to refuse a new vote.

The SNP MP, who is the party’s justice and home affairs spokeswoman at Westminster, argued that if there is a pro-independence majority after next year’s elections, but the Prime Minister persists in failing to agree a second plebiscite, then the Scottish Parliament should continue to push ahead with one.

She made her intervention in a major lecture last night on the eve of the SNP’s annual conference, where delegates will debate a key resolution on independence following a series of polls returning a Yes majority.

The QC also told her online audience that Scotland was “on a highway to independence” and that too many US Democrats take the view that “the UK Government is the last outpost of the Trump project”. And she forecasts that once Scotland votes for independence, a united Ireland will follow.

On Holyrood holding an independence vote, she referred to the First Minister’s Brexit Day speech where Nicola Sturgeon raised this idea if Johnson refused to hand over powers to Holyrood.

However, Sturgeon warned that such a move would be challenged by the UK Government and could “move us forward – but equally it could set us back”.

Cherry, a QC, disagreed. “It is my view that if the pro-independence referendum parties obtain a majority at the Scottish election next year and the PM refuses to come to the table to negotiate a second Edinburgh Agreement, the avenue which the FM contemplated earlier this year should be pursued,” she said, delivering the Wales Centre for Government’s annual lecture.

She added that “it would require a carefully crafted bill to be piloted through Holyrood” and there would be “the inevitable legal challenge”. But she insisted that whatever the outcome, the independence cause would not be damaged and underlined the political context in which any future referendum bid was made.

She also suggested it was “unfortunate” that the debate about a new independence vote was dominated by a focus on “whether or not the UK Government will grant” the transfer of powers to Holyrood.

“It would be for the courts to decide whether the bill passed was within the competence of the Scottish Parliament and, thus, whether the referendum so authorised could proceed...The case would undoubtedly end up in the UK Supreme Court,” she said.

“If they found the bill to be within competence, then we would have a lawful referendum.

“And one which would be hard for Unionists to boycott. If we lost then I do not believe we would be any further back than the stalemate that will ensue if Boris Johnson digs his heels in.”

Cherry also called for the First Minister to publish documents on the new case for independence which would “provide the information and answers people want on how Scotland can make the transition from a Yes vote to becoming an independent country”.

She then gave her views on the potential implications for the Union: “Scottish independence could be the catalyst for the sort of constitutional reform in England which is talked about by the chattering classes. I say England because there is a very real question as to what the UK will consist of after Scotland resumes the status of an independent state.

“I find myself in agreement with John Major in that Scotland will go first then Northern Ireland will follow and reunify with the rest of Ireland.”