THERESA May has ordered her cabinet to “strengthen and sustain the Union” amid growing signs that Nicola Sturgeon intends to call a second independence referendum.

The Prime Minister held a lengthy cabinet discussion in Downing Street on the Union which “touched on” the possibility of another vote, her spokesman confirmed.

The Union and Russia were the main items on Tuesday’s agenda.

Mrs May said she wanted the Union to “stay together” as cabinet secretaries outlined how their departments worked with the administrations in Scotland, Wales and Northern Ireland.

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The SNP said the meeting showed the Conservative government was “clearly rattled” at how it was viewed by voters in Scotland.

Recent reports suggest the UK government is preparing for the First Minister to make a major announcement on a referendum at next month’s SNP conference - possibly naming a date or asking for a transfer of powers to pass a Referendum Bill at Holyrood.

Former FM Alex Salmond has identified autumn 2018 as a workable date.

Ms Sturgeon has said that if the UK government rejects her plan for a bespoke Brexit deal keeping Scotland in the EU single market, a referendum is “all but inevitable”.

With little sign of Downing Street agreeing to such a “differentiated deal” both the Unionist and Nationalist camps are girding themselves for a rematch of 2014.

The Cabinet did not discuss the SNP’s proposal for a Scottish Brexit.

Mrs May’s spokesman said: “The Prime Minister said the government recognized how much we all value the Union, how it had been an incredibly successful partnership. We must continue to point that out.

“She added that everyone around the table wants the union to work and stay together."

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Cabinet Office Ben Gummer then "pointed out it is the most successful political union ever seen, and it is critical we continue to maintain, strengthen and nurture the 300 plus year-old relationship".

Individual cabinet secretaries then talked about their departments’ work and the “importance of maintaining a level of engagement to strengthen and enhance the union going forward”.

The spokesman said that the discussion had focused on the "importance across the whole of government to go out there and listen to and engage with the devolved administrations".

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The discussion "touched on" a second Scottish independence referendum but restated the UK government position that the question was not whether there could be one, but whether there should be.

"No there shouldn’t," the spokesman said.

Whitehall sources later said the meeting was part of Mrs May’s ongoing commitment to the Union rather than an exceptional event, however the heightened political context means no high-level discussion of the constitution can be regarded as routine.

Scottish Secretary David Mundell, who contributed to the session, is likely to face questions from MSPs on the discussion when he appears at Holyrood today.

Mr Mundell is due to discuss the Brexit process at the European Committee.

He insisted on Monday that Scotland would be taken out of the EU by Brexit even if there was a vote for Independence before 2019, a claim designed to undermine the argument that a swift Yes vote to independence would allow Scotland to remain a continuity member of the EU.

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An SNP spokesperson said: “This shows the Tories are clearly rattled at how their actions are being seen by people across Scotland – and they have good reason to be.

“They talk about listening seriously to Scotland, but their actions tell a completely different story – underlined by the fact the UK cabinet failed to discuss the Scottish Government’s compromise proposals on Europe.

“The Tories now seem to think they can do what they want to Scotland and people will simply accept it. They may discover just how wrong they are about that if they continue trying to drag Scotland out of Europe against its democratic will, and in their reckless pursuit of a hard Brexit, which threatens to take Scotland and the rest of the UK off an economic cliff edge, with catastrophic consequences for jobs and livelihoods.”