The next Westminster Government must come under “sustained” and “unrelenting” pressure to give Scotland the power to hold a referendum on its future in the UK, the Scottish Greens have insisted.

Party co-leader Patrick Harvie made the demand as he launched the party’s General Election campaign on Monday.

Speaking to supporters in Stirling, Mr Harvie said the Scottish Green manifesto, due to be published next week, would set out how powers currently held at Westminster could be used to “create a fairer future for all”.

But he added: “The only way we can deliver those plans is for Scotland to be able to choose its own way.

The next UK Government must be under immediate and sustained, unrelenting pressure to make this change

“That starts by Westminster granting the Scottish Parliament the power to hold constitution referendums so the people of Scotland can make their choice about their future at a time of their choosing.”

Mr Harvie insisted: “The next UK Government must be under immediate and sustained, unrelenting pressure to make this change.

“It is our fundamental democratic right and can’t be denied any longer.”

His comments came as he attacked both the Conservatives and the Labour Party – which polls suggest will oust the Tories from government after the July 4 General Election.

Mr Harvie claimed the “real causes of the country’s problems” were “Tory cruelty, Tory incompetence and Tory corruption”.

But he added: “Labour seem to threaten more of the same, from anti-immigrant rhetoric to transphobia.”

He went on to say that “delivering the change that voters and the country so desperately need will take determination and commitment” – before claiming this was “entirely absent from Keir Starmer’s Labour Party”.

He claimed Labour was a party that “promises a change of government but without a change of politics”.

Mr Harvie said: “We’re going to wake up to a new prime minister on July 5 but we will still have austerity and Brexit and the hostile environment.”

His co-leader, Lorna Slater, claimed that Sir Keir, together with Tory leader Rishi Sunak and SNP leader John Swinney, were all either “too scared” to take action to tackle the climate crisis or “too invested in the status quo”.

But, with a record 44 Scottish Green candidates running in the election, she said her party was “providing a real alternative” and “providing hope” for voters.

Ms Slater said: “Decisive action to tackle the climate emergency. That is what is needed and that is what is at stake in this election.”

Adding that the Greens would set out “plans to invest in renewables and the Green industries of the future”, Ms Slater said: “It is the Greens who are being honest with voters about the reality of the climate crisis and what we need to do to build a modern, green and fair Scotland.”