THE “rules” of the UK’s constitution are heading for breakdown as the gulf between the Scottish and Westminster Parliaments grows with Brexit, according to a law expert.

The warning comes after a week in which an independent report outlined how UK ministers will soon have powers to overrule MSPs on areas that are Holyrood’s responsibility under the Brexit Bill – which the SNP described as an “undemocratic power grab”.

Meanwhile, Holyrood voted against the legislation needed to put Boris Johnson’s deal into effect on the basis it was incompatible with Scotland’s desire to stay in the EU.

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Dr Nick McKerrell, senior lecturer in law at Glasgow Caledonian University, said the whole of 2019 was marked by a series of constitutional clashes, such as the prorogation of Parliament.

He said: “These issues are unresolved as the issue of devolution is not resolved.

“There are issues that are done through convention – that is to say it’s not legally binding. So the convention is the Scottish Parliament’s permission should be sought on areas where devolved issues are affected and nine times out of ten that is what has happened over the last 20 years.

“But the areas where it hasn’t happened are issues to do with Brexit, where there is a gulf between what the Scottish Parliament wants and what the UK Parliament wants.

“That is even more now than in 2019, as the UK Parliament has a massive majority in favour of Brexit, whereas the Scottish Parliament has a big majority against Brexit. So the constitutional rules of the game that operate – conventions, polite behaviours and so on – they could all break down, because there isn’t any overlap. Holyrood not giving Westminster permission to do the Bill is an example of that.”

Last week the Scottish Parliament Information Centre (SPICe) said that “powers allow UK ministers, acting alone, to make provision in devolved policy areas” in the Withdrawal Agreement Bill, which passed its final Commons reading last week.

A memorandum by the UK Government says that Tory ministers would “not normally” use such powers without the agreement of the devolved administrations.

McKerrell said the issue hinged around an ongoing dispute over what would happen to powers which are currently held by the EU after Brexit, with a lack of agreement between the Scottish and UK Governments on some areas such as food safety, aspects of agriculture and fishing.

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In 2018, the Scottish Parliament passed an emergency bill on repatriating EU powers in areas such as farming and fishing – but the Supreme Court ruled it unlawful saying Westminster had the ultimate say over EU legislation.

McKerrell said: “What [the Bill] is saying is the Scottish Government will have power under the Brexit deal to deal with devolved matters that deal with Europe – however, so will UK ministers.

“Theoretically what exists now is for the UK Government to pass delegated legislation on these issues themselves.

“Formally they say they wouldn’t do that, they say they would wait for agreement from the Scottish Government. But it does theoretically give them that power. However it’s not in all areas – it is in areas where there is a dispute about whether it is devolved or not.”