THE prospect of a UK-wide constitutional crisis has been raised after the Scottish Government joined forces with the Welsh Government to draw up amendments to Theresa May’s flagship Brexit Bill they believe is an "unashamed move to centralise decision-making power in Westminster".

Nicola Sturgeon met her Welsh counterpart, Labour’s Carwyn Jones, in Edinburgh on Monday and discussed their "alternative proposals" to the European Union Withdrawal Bill, aimed at protecting devolved powers.

The legislation aims to transpose EU law into British law so that the same rules apply on the day of Brexit as the day before and involves EU responsibilities in devolved areas being initially transferred to Westminster.

The UK Government has said this will allow common frameworks to be put in place where necessary before further devolution can take place.

However, both the Scottish and Welsh Governments believe this is tantamount to a "power-grab".

In contrast, David Mundell, the Scottish Secretary, has dismissed such an assertion and has insisted rather than a power-grab, the UK Government is intent on giving Scotland a “powers bonanza” post Brexit.

“No one in Whitehall wants to have control over Scottish hill-farming. It’s absurd,” noted one UK Government source.

Last month, Ms Sturgeon and Mr Jones joined forces to oppose the bill when it was, saying they would not recommend their governments granting legislative consent to the Bill as it stood.

In a joint statement following their meeting on Tuesday, the FMs said the approach of the UK Government since the Brexit vote was "a rejection of the principle of devolution".

They said: "Most seriously, the UK Government's EU Withdrawal Bill is an unashamed move to centralise decision-making power in Westminster, cutting directly across current devolved powers and responsibilities.

"The Scottish and Welsh Governments have already made clear that they cannot recommend that the Scottish Parliament and National Assembly give their necessary legislative consent to the Bill.

"We believe that the Bill must not be allowed to progress in its current form.”

The two administrations said that to provide a constructive way forward, they were now working to agree potential amendments to the Bill, which will address their concerns. They also explained that they were co-ordinating their advice to parliamentarians in Edinburgh and Cardiff to ensure they fully understood the Governments’ concerns and their alternative proposals.

"It will now be for the UK Government to respond positively to our suggested amendments to move negotiations forward and ensure there is a functioning legal system on withdrawal from the EU and agreed UK structures - where these are required - that reflect the views and interests of all parts of the UK, and respect devolved powers and responsibilities," they added.

MPs are due to start their first debate on the flagship legislation on Thursday September 7 with sources saying the key vote on its Second Reading is due to take place the week after.

Earlier this month, Damian Green, the First Secretary of State, together with Mr Mundell met John Swinney, the Deputy First Minister, and Michael Russell, the Scottish Government’s Brexit minister, in bilateral talks in Edinburgh to resolve the political impasse over the Bill but were unsuccessful.

Whitehall sources have suggested Mr Green is seeking more talks ahead of the key Commons vote, which could be tight given the UK Government has, with the help of Northern Ireland’s Democratic Unionists, a working majority of just 13.

While Holyrood cannot veto the Brexit bill, if the PM decides to proceed with the legislation without the consent of MSPs, a constitutional crisis would result.

Some of the Nationalists’ opponents at Westminster believe the SNP is intent on provoking such a confrontation as they feel this would, in the current climate, be the only thing that would give the campaign for a second independence referendum fresh momentum.