RELATIONS between the Prime Minister and First Minister continued to deteriorate after Downing Street yesterday announced the date at which Article 50 would be triggered – without telling the Scottish Government.

Nicola Sturgeon hit out during her Bute House press conference last week saying she hadn’t been told the day the official Brexit process would begin, after speculation mounted it would be on March 15. But yesterday, after Downing Street announced Article 50 would be invoked next Wednesday, March 29, it was clear, a week on, the First Minister still hadn’t been informed.

Comments from her official spokesman revealed her anger. He told The National: “The fact the UK Government failed to properly and fully inform all of the devolved administrations on the plans for triggering Article 50 speaks volumes – and totally exposes as empty rhetoric Westminster’s language about equal partnership.”

Earlier yesterday, Michael Russell said he only found out the process of leaving the European Union would formally get under way on March 29 when it was reported by the BBC.

The Scottish Brexit Minister has been involved in discussions between London and Edinburgh over the Article 50 process as a member of the Joint Ministerial Committee (EU Negotiations), which the UK Government set up to ensure the devolved administrations would be involved in the process.

But Russell claimed he had not been informed by Downing Street about the Prime Minister’s intended date for triggering Article 50.

Sir Tim Barrow, Britain’s ambassador to the EU, informed the office of European Council President Donald Tusk yesterday morning of the Prime Minister’s plans to trigger Article 50 on March 29. The two-year nego- tiation and ratification process means the UK will leave the bloc on March 29, 2019. Russell tweeted: “Thank you @BBCNews for letting JMC members like me know that #Article50 is to be triggered next week. @GOVUK somehow forgot to inform us.”

That led to other SNP politicians accusing the Conservative administration of “arrogance” and a “complete dismissal of Scottish interests”.

Martin Docherty, MP for West Dunbartonshire, said on Twitter: “In the entire process this is extra- ordinary #Brexit chaos #Article50.”

Colleague Roger Mullin, who represents Kirkcaldy and Cowdenbeath, posted: “Outrageous but typical of UK government arrogance and complete dismissal of Scottish interests. #indyref2.”

The row comes amid increasing tension between Edinburgh and London over Brexit after the First Minister announced plans to seek to hold a second independence referendum in the wake of the vote to quit the European Union. There is also frustration in the Scottish Government that no formal response has been given to its plans, published in December, that would allow Scotland to remain in the European single market while still a part of the UK.

While the UK as whole backed exiting the EU, 62 per cent of voters north of the Border wanted to remain. Scottish Government ministers insist the result gives them a “cast-iron mandate” to stage a second independence referendum, after the party’s manifesto for last year’s Holyrood elections said such a vote should be held if there was a “material change in circumstances”

from the 2014 ballot, citing the example of Scotland being removed from the EU against its wishes.

The First Minister wants a referndum held between autumn 2018, when the Brexit terms will be known, and spring 2019 when the UK leaves the bloc. However, Theresa May has indicated she will not consent to Holyrood being given powers to hold a referendum, saying “now is not the time”.

Responding to the announcement of the date at which Article 50 will be triggered, Tusk tweeted: “Within 48 hours of the UK triggering Article 50, I will present the draft #Brexit guidelines to the EU27 Member States.”

An extraordinary summit of the remaining 27 EU member states is due to be called within four to six weeks after Article 50 is triggered.

That summit will draw up a mandate for the European Commission’s chief negotiator, Michel Barnier, probably allowing talks to begin in earnest in May.

Notification of the historic step will come in the form of a letter from the Prime Minister to Tusk, though Downing Street did not make clear whether this would be a physical letter handed to the European Council president by a UK representative or might be sent electronically.

It will be the first time that the provisions of Article 50 – which sets out the process for any EU member state “to withdraw from the Union in accordance with its own constit- utional requirements” – have been activated.

Notification comes 279 days after the referendum of June 23 last year delivered a 52 per cent to 48 per cent overall majority in favour of withdrawal.

However, only England and Wales voted in favour of leaving, with Northern Ireland joining Scotland in against.

May, who was visiting Swansea yesterday, is expected to visit all four UK nations before notification takes place. The PM’s official spokesman said: “Earlier this morning, the UK permanent representative to the EU informed the office of Donald Tusk that it is the UK’s intention to trigger Article 50 on March 29.”

Asked about the failure to give Russell prior notice of the date on which Article 50 will be triggered, a spokesman said there was no statement on the matter.