WESTMINSTER is heading for a constitutional crisis unless the UK Government “pulls its finger out” and protects the devolved settlement in the wake of the Brexit Bill, senior SNP figures have warned.

After a meeting of the Inter-parliamentary Panel on Brexit, involving committee chairmen from Westminster and Holyrood, the SNP’s Bruce Crawford, convener of the Scottish Parliament’s Finance and Constitution Committee, suggested time was now running out for Theresa May to deal with cross-party concerns that the EU Withdrawal Bill is nothing more than a “power-grab” by Whitehall, which fundamentally undermines the devolution settlement.

“My understanding is that the words to the new amendments have not yet been shared with the Scottish Government. The ball is clearly in the UK Government’s court and now is the time for urgent action,” declared Mr Crawford.

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A senior Nationalist colleague warned that, as things stood, Holyrood would not give its consent to the passage of the bill. “I can’t see how it can. The UK Government needs to pull its finger out,” he said.

Much anger and dismay have been expressed by all parties, including the Scottish Conservatives, about the way the process has been handled; most specifically about how UK ministers failed to honour their promise to amend the bill in the Commons. It will now be amended in the Lords but this means MPs will have no input into the debate.

The bill is due to begin its passage through the Upper House at the end of this month. The key point will come after the Report Stage and before Third Reading - the final vote - when the legislation goes to Edinburgh and Cardiff for MSPs and AMs to give their consent; or not.

“The House of Lords see themselves as the guardians of the constitution,” said Mr Crawford. “If the Scottish Parliament and Welsh Assembly were to reject giving Legislative Consent Motions, then that would put the House of Lords in a very difficult position. They would have to think very carefully about what they do.”

Already peers have pointed to the possibility of the Lords, in the face of Holyrood withholding its consent, refusing to pass the bill.

Labour’s Lord Foulkes, the former Scotland Office Minister, said: “People say the House of Lords has no legitimacy but if there is no Legislative Consent Motion, then we could say we would be doing what the Scottish Parliament wants us to do."

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Mr Crawford said a scenario where peers declined to give the bill a Third Reading was “entirely possible”.

Asked if Westminster was now facing a constitutional crisis, he replied: “That’s the potential that’s there. The UK Government has it in its own hands to get itself out of a hole. It should do it.”

However, his deputy on the Holyrood committee, the Conservatives’ Adam Tomkins, took a different, more sanguine view, arguing that a constitutional crisis could be averted because both governments essentially wanted the same thing.

Describing the panel’s talks as “very positive and constructive,” he explained how there had been a “significant intensification at official level since the turn of the year”. He insisted: “Significant progress has been made.”

Mr Tomkins also acknowledged the Lords was in a difficult situation regarding the bill but he did not think they would be put in a position where they could reject it.

“I can’t imagine the Government will allow that to happen. Both governments want a common frameworks solution; politically they want the same thing. Secondly, look at the polls; Scotland is not in the mood for another constitutional crisis,” he insisted.

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The Inter-parliamentary Panel was formed last year and its meeting in the House of Lords was attended by conveners and their deputies from three Holyrood committees as well as the chairmen of the Lords EU and Constitution Committees.

Chloe Smith, the new UK Constitution Minister, was also in attendance – “listening very patiently and attentively” - as was Bernard Jenkin, who chairs the Commons Brexit Committee, and Sir Bill Cash, who chairs the Commons European Scrutiny Committee.

The Lords Constitution Committee is expected to publish a report on the Withdrawal Bill next week.