NICOLA Sturgeon has upped the ante on Scotland’s future, warning Theresa May that her Brexit plan for Britain makes a second independence referendum all but inevitable.

The First Minister said the Prime Minister’s proposal for the United Kingdom to leave the European Union’s single market and customs union threatened to be “economically catastrophic".

“It seems the Westminster Tory Government now think they can do anything to Scotland and get away with it. They must start to understand how wrong they are,” declared Ms Sturgeon.

Read more: Alison Rowat - May’s ‘one out, all out’ puts the pressure on Sturgeon

“The UK Government cannot be allowed to take us out of the EU and the single market, regardless of the impact on our economy, jobs, living standards and our reputation as an open, tolerant country, without Scotland having the ability to choose between that and a different future.”

She added: “With her comments today, the Prime Minister has only succeeded in making that choice more likely.”

Asked later if a second independence poll was now all but inevitable, the FM replied: "That is very likely the case."

David Mundell called for a “united front” between London and Edinburgh, warning that any division at home would simply advantage the other 27 member states in the negotiations. “Therefore,” he insisted, “what we need to ensure is: there isn’t.”

The Scottish Secretary, who alongside an SNP Government minister will attend the Joint Ministerial Committee[JMC] on Brexit on Thursday, said: “It is not about getting hung up on the semantics of the single market. It is about getting the best outcome for Scottish businesses to be able to trade without barriers and tariffs with EU. I hope the Scottish Government will ultimately recognise that.”

His remarks were echoed by Ruth Davidson and Kezia Dugdale.

The Scottish Conservative leader said: “Nicola Sturgeon should now rule a second referendum out and instead work to get the best deal out of Brexit for all of us across the UK."

The Scottish Labour leader, who said the PM’s plan would make Britain a "more insular nation" with increased division, also called on the FM to rule out a second vote on Scotland’s future.

Read more: Alison Rowat - May’s ‘one out, all out’ puts the pressure on Sturgeon

"Under independence, Scotland would face the prospect of being out of the EU and out of the UK. That would be a disaster for Scotland," she insisted.

Mrs May had briefed Ms Sturgeon ahead of her speech and last night spoke to Jean-Claude Juncker, President of the European Commission, and Donald Tusk, President of the European Council, as well as Angela Merkel, the German Chancellor, and Francois Hollande, the French President. The PM is due to have talks with business leaders when she attends the World Economic Forum in Davos, Switzerland, today and tomorrow.

“Chancellor Merkel and President Hollande both welcomed the Prime Minister’s commitment to the continuing strength of the EU and her intention to negotiate a new partnership with the EU when it leaves,” said a Downing Street spokesman.

Earlier, in the grand surroundings of Lancaster House near Buckingham Palace, Mrs May set out her “Plan for Britain” before an audience of foreign ambassadors and diplomats.

In a 40-minute speech setting out her 12 key objectives for EU withdrawal, she announced Britain would leave the single market and seek a "bold and ambitious" free trade agreement to allow it to continue doing business with its 27 former partners without having to pay "huge sums" into EU budgets.

She confirmed she wanted to take the UK out of the jurisdiction of the European Court of Justice and restore control over immigration.

The PM also signalled that she wanted a new arrangement on customs to ensure "frictionless" cross-border trade; she said she had an "open mind" on whether this should be done through associate membership of the current customs union or a completely new customs agreement.

She explained how she wanted to avoid a “cliff edge” situation once a deal had been agreed and pointed to some kind of transitional arrangement for certain sectors.

Mrs May also announced MPs and peers would be given a vote on the final deal reached with the EU.

She said she was "confident" a trade deal and a new strategic partnership with Brussels could be achieved within the two-year deadline set out in Article 50, insisting a good deal for Britain would also be good for Europe.

Read more: Alison Rowat - May’s ‘one out, all out’ puts the pressure on Sturgeon

But the PM warned: "I know there are some voices calling for a punitive deal that punishes Britain and discourages other countries from taking the same path. That would be an act of calamitous self-harm for the countries of Europe. And it would not be the act of a friend."

She made clear: “No deal for Britain is better than a bad deal for Britain."

But the Conservative leader insisted her plan would create "a truly global Britain...a great, global trading nation that is respected around the world and strong, confident and united at home".

However, Jeremy Corbyn, the Labour leader, warned her plan would turn the UK into a "low-corporate taxation, bargain basement economy" if the EU did not give her everything she wanted.

In Brussels, Guy Verhofstadt, the European Parliament’s chief Brexit negotiator, welcomed Mrs May’s clarity but warned: “The days of UK cherry-picking and Europe a la carte are over.”

He added: “Threatening to turn the UK into a deregulated tax heaven will not only hurt British people, it is a counter-productive negotiating tactic.”

The markets reacted positively to the PM's speech. The pound rose almost three per cent to about 1.24 US dollars after slumping below 1.20 on Monday as speculation grew the UK would be leaving the single market.

In the Commons, David Davis, the Brexit Secretary, told MPs the promised vote on the final deal would not be an opportunity for MPs to prevent withdrawal as defeat for the UK Government would not mean Britain staying in the EU but, rather, leaving it without a deal.

In exchanges, the SNP MP Peter Grant accused Mrs May of subjecting Scotland to a series of "worthless Westminster promises", including one that a No vote in 2014 would keep Scotland in the EU.

The Glenrothes MP told Mr Davis: "I have to say to you, I hope you'll pass the message back to your boss that if she insists on giving Scotland only one option to remain in the European Union, Scotland will take that up."

Mr Davis stressed how the Scottish Government’s options paper would be given full consideration at this week’s JMC. He said there were parts he agreed with such as on protecting workers’ rights, and parts he did not.

The Secretary of State said some people might be surprised by how "pro-devolution" he was, adding: "There will be nothing taken away from devolved administrations and, indeed, we have to decide what passes to them from the European Union."

Meantime at Holyrood, MSPs backed SNP Government proposals to keep Scotland in the single market after Fiona Hyslop, the External Affairs Secretary, urged them to "stand up for Scotland's interests".

Labour backed the SNP to defeat the Tories and Lib Dems on the issue but on the condition that any bespoke Scottish alternative to a hard Brexit should be within the UK.