THE Welsh Government has warned Boris Johnson that his post-Brexit power-grab legislation will “accelerate the break-up of the Union”.

In a furious letter UK Business Secretary Alok Sharma the pro-Union, Labour-led administration in Cardiff said the proposals in the Internal Market Bill would weaken the current rights of the devolved institutions.

Ministers in London claim the devolved administrations are on course for extra responsibilities after the UK leaves the EU. But as this could lead to different regulatory regimes in the UK, the Tory Government has drawn up a trade bill to underpin the so-called internal market.

At the heart of that is a “mutual recognition” mechanism. This would see regulations in one part of the UK recognised in all the other nations.

This would, in effect, allow Westminster to impose lower standards on food safety and environmental protections in Scotland, Wales and Northern Ireland.

In his letter to the Tory minister, Welsh Brexit Minister Jeremy Miles said: “The Welsh Government is concerned that the long-term survival of the United Kingdom is under great strain and that the approach taken in the white paper will exacerbate those tensions in a way which, if not addressed, will accelerate the break-up of the Union.”

Miles said the Welsh administration’s initial view that the paper was “fundamentally flawed and misleading” had been confirmed by subsequent detailed analysis.

He added that the proposed approach from the Westminster Government, if followed through, would “represent a direct attack on the current model of devolution” and “emasculate the current rights of the devolved institutions to implement changes to the regulatory environment”.

He concluded that the Westminster legislation envisaged in the white paper was “unnecessary, unworkable [and] heavy-handed” and would not secure consent from the Welsh Parliament.

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Earlier this week, Holyrood passed a motion calling the UK Government’s proposals “incompatible with devolution and the democratic accountability of the Scottish Parliament”.

The legislation would, MSPs said, “fundamentally undermine legitimate devolved policy choices on a range of matters, including the environment, public health and social protections”.

Only the Tories voted against, with the motion passed by 92 votes to 31.

A UK Government spokesperson said: “Our proposals ensure businesses can continue to prosper after the transition period ends by guaranteeing their ability to trade freely with each nation of the UK as they have done for centuries.

“Under our plans the devolved administrations will have power over more issues than they have ever had before and will continue to have the power to regulate within their nations.”

The spokesman insisted existing EU standards would “be retained in our domestic law and we will not sign any trade deal that compromises our high standards” after Brexit.