WHITEHALL has intensified the political stand-off with Edinburgh over Brexit, making clear that it will move “no further” on its flagship legislation, meaning a constitutional crisis now looks inevitable.

At the weekend Nicola Sturgeon dug her heels in, insisting she would “not compromise” on what she sees as the principle of devolution; that all 111 powers and responsibilities being transferred from Brussels post Brexit should go directly to Holyrood.

She explained: “There is an issue of principle at stake that we won't compromise on because if we did, we would allow Westminster to exercise a power-grab on the responsibilities of the Scottish Parliament and I don't think any First Minister worth their salt should agree to that.”

Brexit analysis: PM and FM in stand-off over EU Withdrawal Bill powers

But the UK Government, having moved to accept that 86 powers and responsibilities would go straight to the Scottish Parliament, wants to “freeze” temporarily 25 others so that common UK-wide frameworks can be agreed.

It says it wants a “safety brake” to ensure that in the time it takes to agree common frameworks on issues like agriculture, fishing and environmental protection - probably extending over several months - the First Minister and her colleagues do not in this period introduce changes that could undermine the UK’s internal market.

A Whitehall source close to the talks said: “I don’t sense us moving from our position. We have already moved a hell of a long way and we can’t move any further in the way the Scottish Government wants us to do. We’re still talking and officials are working hard to find a way through but I don’t know whether we can now bridge that gap.”

At the weekend, Michael Russell, the Scottish Government’s Brexit Minister, suggested that the deadlock came down to a single word: “agree” to rather than “consult” on the frameworks.

Brexit analysis: PM and FM in stand-off over EU Withdrawal Bill powers

But the UK Government believes that any veto Holyrood would have over its role in protecting the integrity of the UK-wide market would be a step too far. “This,” insisted one source, “would be giving away too much.”

Talks involving Mr Russell and David Lidington, Theresa May’s de facto deputy, are due to resume on Thursday but no breakthrough is expected; rather, a key moment will come next Wednesday when the Prime Minister chairs a meeting of the Joint Ministerial Council, where she will sit across the table from Ms Sturgeon.

While UK ministers are hoping to get agreement from their Scottish counterparts on their proposed changes to the EU Withdrawal Bill by the end of the committee stage in the Lords later this month, there is still an option to amend it at report stage, which could run to as late as May before it has to go to Edinburgh for MSPs to give or withhold their consent.

If no agreement is given, then Mrs May and her colleagues believe the issue will end up in the “court of public opinion” as to who is to blame for the constitutional deadlock and are confident most Scottish voters will not point the finger at them.

In the Commons, the PM, making a statement on her Brexit speech, told MPs that the country could “not escape the complexity of the task ahead” yet with “pragmatism, calm and patient discussion, I am confident we can set an example to the world”.

Mrs May accepted there would be ups and downs in the coming months but insisted: “We will not be buffeted by the demands to talk tough or threaten or walk out. And we will not give in to the counsels of despair that this simply cannot be done, for this is in both the UK's and EU's interests."

Brexit analysis: PM and FM in stand-off over EU Withdrawal Bill powers

But Jeremy Corbyn berated the Tory Government for the "20 wasted months" since the EU referendum during which the "arrogance" of some Cabinet ministers, who bragged it would be the "easiest deal in history," had turned into "debilitating infighting".

The Labour leader argued: "Her speech on Friday promised to unite the nation but it barely papered over the cracks in her own party."

Ian Blackford for the SNP complained about the absence of Scottish Secretary David Mundell from the recent Brexit strategy meeting at Chequers, claiming it showed a “flagrant disregard by this Government for the nations that make up the United Kingdom”.

Today, the PM, Mr Lidington and David Davis, the Brexit Secretary, will hold talks in Downing Street with Guy Verhofstadt, the European Parliament’s chief co-ordinator, while in Brussels Michel Barnier, the EU’s chief negotiator, is due to meet Arlene Foster, the Democratic Unionist leader.

As officials resume the UK-EU negotiations this week, today a key moment will come when the EU27 publishes its draft negotiating guidelines for a post-Brexit trade deal.

Yesterday evening, Chancellor Philip Hammond told MPs some £700 million had now been spent on Brexit preparations “for a full range of outcomes”. Another £3 billion has been earmarked.