Alex Salmond’s Alba party is proposing to “break the constitutional logjam” by holding a vote on whether Holyrood should have the power to “legislate and negotiate for independence”. 

Ash Regan, the party’s sole MSP, said she intended to introduce a member’s Bill to consult the people of Scotland on extending the powers of the Scottish Parliament.

Last year, the UK Supreme Court ruled that Holyrood could not hold Indyref2 without Westminster’s consent, as the Union was a reserved issue.

However, Ms Regan said she believed it would still be legal to hold a referendum asking people whether they believed “the powers of the Parliament should be extended to include the right to legislate for and negotiate independence”.

She said if Holyrood approved the plan, she wanted to go to the country on September 19 next year, ten years after the 2014 vote.

Alba said the plan was based on an opinion by Aidan O’Neill KC, who said asking people their opinion on Holyrood’s decision making powers was “arguably within competence”. 

The idea has almost no chance of becoming law, as it would require cross-party support from at least 18 other MSPs to advance beyond the initial proposal stage

But if the SNP and Greens refuse to back it, Alba will be able to use that as a stick to beat them and accuse them of backsliding on independence.

The proposal could smoke out any more potential converts to Alba within the SNP.

Tekllingly, both Ms Regan and Mr Salmond urged the Scottish Government to adopt the Bill, almost certainly knowing it would not.

Any referendum intended to deliver independence could also be regarded as a de facto Indyref2, and so outwith Holyrood’s powers and liable to a Supreme Court challenge.  

Even if held and backed by the electorate, the UK Government would not be compelled to cede power to Holyrood, just as it has refused SNP election mandates to do so.

To hit her September 19 date, the Bill would need to pass by the  end of June and the summer recess, another very tall order.  

Ms Regan previously suggested "independence thermometers" around Scotland would help end the Union when she ran for the SNP leadership earlier this year and came third.

A former SNP minister who defected to Alba last month, she said: “It is Alba Party’s policy that at each and every election Scotland should be offered the choice of voting for a mandate to negotiate independence. 

“That is unlikely to happen at the coming General Election since neither the SNP or the Greens support that proposition and have rejected the Alba Party offer of a single Scotland United candidate standing in each constituency seeking that mandate. 

“However, there is no reason why the independence movement should make no progress in the meantime. 

“My colleague Neale Hanvey MP has a Scottish sovereignty Bill currently before the Westminster Parliament which would transfer the power to hold a referendum on independence to Scotland.

“But the real prospect of momentum lies here in Scotland. 

“Last year’s ill-fated expedition to the Supreme Court has halted the opportunity to propose an independence referendum in the Scottish Parliament. 

“However, there is nothing to stop our Parliament proposing a referendum which we believe would be within competence, and that is to ask the people whether they believe the powers of the Parliament should be extended to include the right to legislate for and negotiate independence.

“That is what my proposed new draft Bill does and I intend to canvass public and parliamentary support for it now. It is time for the independence movement to offer our supporters the real  prospect of progress.”

Launching her plan to the media, Ms Regan was asked how the powers being being sought should be used if her plan worked.

She said: "I think that certainly will attract international popular attention, and I see this as a next step on the road to Scotland becoming an independent country.

"Let's say there was a Yes vote in this, then in the next election, which could be quite soon after that, and there was a mandate and a clear instruction given by the people of Scotland that we got over the 50% , then that would be a very clear instruction from the Scottish people that they expected us to negotiate straightaway for Scotland to become independent.

"So it's like adding another layer of democracy and clarity on that initiative."

Mr Salmond, the former first minister and now Alba leader, added: “This proposal can propel the independence movement forward and free it of its current inertia.

“If you want to end a London veto over Scottish sovereignty then you have to make it clear that you are not prepared to take No for an answer.

The way to assert the sovereignty of the Scottish people is to ask the people the question on whether their own parliament should have the powers to determine our future.”

Alba party Chair Tasmina Ahmed-Sheikh added: “The legislation proposed goes right to the heart of the issue. There can be no better initiative to take on this St Andrew’s Day.”