By Jim Sillars, former SNP MP and deputy leader of the party.

I AM on the outer fringes of the SNP but recognise its importance to the independence movement. Watching the party self inflict an electoral wound, through constant demands for a second independence referendum arising out of a complete misinterpretation of the EU referendum result, has been painful.

I fear we may be about to witness further self-harm. Threatening to veto the Repeal Bill taking the UK out of the EU, by refusing a Legislative Consent Motion under the Sewel Convention, would be a serious mistake by demanding what the SNP Government cannot deliver. If the veto threat continues throughout EU negotiations, it will raise expectations to an impossible height, only for them to deflate, leading to further electoral setbacks.

I do not underrate the importance to Scotland, Wales and Northern Ireland of the EU talks and, while no friend of the UK Government, I can see why it will not include them in the UK negotiating team. The die was cast last year, when Nicola Sturgeon set out to differentiate Scotland, in the eyes of Brussels, from the rest of the UK. So, when hard negotiations get under way, the UK Government would be daft to let a potential Brussels cuckoo into the nest. A short-term tactic that played well in Brussels fell flat in London, where Scotland really needs leverage.

Short-term PR gains leading to longer-term strategic losses have been a feature of the Sturgeon leadership. One example was the decision to contest Article 50 at the Supreme Court. There was no need to do so. The issue was solely on the Royal Prerogative. By sending in the Lord Advocate to argue Sewel, the Supreme Court dealt it a death blow as to whether the Scottish Parliament could hold a veto over UK withdrawal from the EU. Crucially, the Supreme Court, pointed to Section 28(7) of the 1998 Act setting up the Scottish Parliament, stating that it did “not affect the power of the Parliament of the United Kingdom to make laws for Scotland”. It also pointed out that the Westminster Act of 2008, incorporating the Treaty of Lisbon, which affected the competencies of the devolved administrations, was not subject to consent motions.

The concept of a Scottish veto was crushed by Section 150 of the Supreme Court judgment, which noted that the Lord Advocate and Counsel General for Wales were “correct to acknowledge that the Scottish Parliament and the Welsh Assembly did not have a legal veto on the United Kingdom’s withdrawal from the European Union”.

The Sewel Convention is a political, not a legal requirement. The inability of my SNP parliamentary colleagues to read and understand legislation or to differentiate between legislation and convention is worrying. The Great Repeal Bill’s purpose is to take us out of the EU. It assumes the same status and becomes reserved to Westminster. I don’t like it but that was the Scottish decision in 2014 and the political and legal reality.

If Ms Sturgeon had not sent the Lord Advocate to argue the relevance of the Sewel Convention in regard to Scotland, we would not have had a definitive ruling against it, so there would be uncertainty that could have been used as leverage against the May Government. Instead another line in the sand was washed away, leaving future threats looking increasingly empty and hollow.

The time for grandstanding is over. Scotland’s interests will best be served by building a wide consensus of national support for powers held in Brussels to come to Edinburgh. If the First Minister chases that objective to embrace Remainers and Leavers, Yes and the No voters, she may yet recover what has been lost of her standing in our nation’s eyes.