THE SNP leadership is hopeful an eleventh-hour deal with Theresa May can still be agreed on her flagship Brexit Bill and does not accept that the one endorsed by the Welsh Government is the Prime Minister’s final offer.

More intergovernmental talks are pencilled in for next Wednesday but Whitehall sources again made clear that unless Nicola Sturgeon and her colleagues moved on their demands, the UK Government would press ahead with the EU Withdrawal Bill without the consent of MSPs, sparking a constitutional clash.

May 18, the date of Third Reading in the House of Lords, is the ultimate deadline for any agreement between London and Edinburgh.

Asked if the Welsh Government had shot the SNP’s fox and left it isolated, Ian Blackford, the Nationalist leader at Westminster insisted: “It remains our preference to reach agreement.”

He explained: “We’ve always said we absolutely recognise the importance of framework agreements and we would not unreasonably withhold consent but we can’t be put into a situation where the principles of devolution, which so many people worked so hard to deliver, are undermined.

“It’s regrettable the Welsh Government has accepted what is currently on the table from the UK Government; it is does not respect devolution. You play with fire when you do not respect the integrity of devolution,” he declared.

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Whitehall sources have made clear “that’s it” in terms of concessions on the bill, pointing out to give any more now would jeopardise the deal with Cardiff.

Asked if he believed Mrs May had indeed made her final take-it-or-leave-it offer, the Highland MP declared: “Absolutely not.

“I know[this is] the language they are using today but we are having meetings next week. I would appeal to the UK Government...let’s see if we can get agreement on this; it’s incumbent on both sides to do that. We are seriously wanting to get there,” he added.

As the UK Government produced a raft of papers on its deal with Cardiff, political sparks flew at Scottish Questions in the Commons.

Asked by Scottish Labour’s Lesley Laird about reports the First Minister had vetoed a deal last week, David Mundell replied: “To be fair to Mike Russell, he has never led us to believe that there was any decision-maker in the Scottish Government other than Nicola Sturgeon.”

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To Nationalist barracking, Ross Thomson, the Tory MP for Aberdeen South, contended: “Nicola Sturgeon’s belligerence in snubbing an agreement on Clause 11 reminds us that the SNP believes in independence, manufactured grievance and a narrow Nationalist agenda, which will always come before the good of the country.”

The Scottish Secretary argued that the last 24 hours had shown the difference between Cardiff and Edinburgh was that “the Welsh Government believe in devolution and the Scottish Government believe in independence”.

The SNP’s Pete Wishart told MPs: “It comes as no surprise to us that Welsh Labour has so easily capitulated to the Tories on this issue. We will never stop defending the integrity of our parliament and we will never allow the Tories to diminish our parliament’s powers.”

Mr Mundell replied: “Our door is open. We hope that we will have direct discussions with the Scottish Government next week, and we hope that they will change their position and sign up, as the Welsh Government have, to proposals that protect the devolution settlement.”

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At PMQs, Theresa May also urged the Scottish Government to reconsider its opposition to the Brexit legislation in the wake of "considerable changes" made by the UK Government.

Her de facto deputy David Lidington addressed peers yesterday evening, telling them the agreement with Cardiff “provides maximum reassurance and certainty” for the devolved settlement.

In a letter to the Cabinet Office Minister, Mark Drakeford, the Welsh Finance Secretary, said the agreement and the new UK Government amendments to the bill represented a “substantive change in approach that balances our concerns on the risks to our devolution settlement and your position to seek certainty in law as we leave the European Union”.

The intergovernmental agreement the Welsh Government has signed up to includes:

- a commitment to “respect constitutional conventions and practices” and to seek to proceed by agreement;

-EU law should be “temporarily preserved” ie devolution suspended where it is thought future UK-wide frameworks underpinned by law will be needed;

- the UK Government will “not normally” be asked to approve Clause 11 regulations without the consent of Holyrood and Cardiff Bay;

-the power to make Clause 11 regulations will expire two years after exit day while the temporary Clause 11 regulations themselves will last for a maximum of five years after they come into force and

- in the “interests of transparency and accountability,” UK ministers will have a duty to report regularly to Westminster on the progress of implementing common frameworks and removing temporary Clause 11 regulations and powers