SENIOR legal figures have warned the UK Government will have difficulty finding a new top law officer for Scotland who is prepared to accept what is now a “reputation ruining” position.

Lord Keen of Elie QC resigned as Advocate General for Scotland last week over controversial Brexit legislation.

It came after Northern Ireland Secretary Brandon Lewis sparked an outcry when he admitted proposals in the UK Internal Market (UKIM) Bill to override sections of the Brexit divorce deal would break international law in a “specific and limited way”.

Former Scottish Tory chairman Keen said he found it “increasingly difficult to reconcile his obligations as a law officer” with the UK Government’s policy intentions in the bill.

His resignation letter to Boris Johnson stated: “Your government faces challenges on a number of fronts and I fear the UKIM Bill in its present form will not make these any easier.”

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Lord Jim Wallace of Tankerness QC, who held the post of Advocate General from 2010-2015, told the Sunday National he shared concerns about a deliberate breach of international law.

He said: “I believe Richard Keen did the right and honourable thing in resigning.

“As to a successor – if the UK Government insists on a policy which it admits is a breach of international law, it may well be difficult to find a credible successor.

“Signing up to a policy of breaking the law isn’t usually a good career move for a serious lawyer.”

Edinburgh-based QC Jonathan Mitchell said Keen’s resignation was not a surprise.

“I think it absolutely must have stuck in his craw to be handed this poisoned chalice,” he said.

“He sees all that is wrong with [the bill] and they just wouldn’t listen – it is the classic lawyer’s problem, you have a client who just won’t accept what you say.

“So I think what he was stuck with was that this was a reputation ruining position and it would just have got worse and worse.”

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He added: “I thought it was totally unsurprising he walked out when he did and it gives them an absolute can of worms exploding over the desk.

“The language of his letter of resignation is scathing – in particular when he says that there was no respectable legal justification for the position it is an attack on the remaining law officers, but it is also a pre-emptive strike in advance against anybody who might come in.”

The sections of the legislation causing concern would give the UK powers to override previous agreements with the EU on the movement of goods between Northern Ireland and Britain and subsidies for Northern Irish companies.

Keen is not the first to resign over the issue, with the head of the UK Government's legal department Sir Jonathan Jones also stepping down.

And on Friday prominent human rights barrister Amal Clooney quit as Britain’s special envoy on media freedom in protest at the UK Government’s “lamentable” decision to override the Brexit divorce settlement.

She said the action threatened “to embolden autocratic regimes that violate international law with devastating consequences all over the world”.

The Attorney General for England and Wales Suella Braverman and Robert Buckland the Justice Secretary and Lord Chancellor have also faced calls to resign over the UKIM Bill.

Following Keen’s resignation, the Conservatives were keen to insist a new Advocate General can be found.

Scottish Tory leader Douglas Ross said he believed there would be a “number of good candidates” for the Government to look at for Keen’s replacement.

In the House of Commons Jacob Rees-Mogg was asked by SNP MP Tommy Sheppard if he believed the Government would be able to find a “qualified law officer in Scotland who will be prepared to countenance breaking the law in future?”

The Tory MP responded: “I’m sure there are many brilliant Scottish lawyers who can be found who can be asked to fulfil the role of Advocate General.

“The pool of wisdom in Scottish legal circles is very deep and I have absolute confidence that we will find someone of comparable genius to the noble lord to take the role that has been vacated.”

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However, SNP MP Joanna Cherry QC said Keen had answered the question of “whether any law officer worth their salt can remain a minister in the Johnson Government”.

Mitchell said while a new Advocate General would not have to be appointed straight away, it could present a “real problem” for Boris Johnson.

“In the long run you can’t live without an Advocate General in the UK Government – they can’t just say well we are not going to bother,” he said.

“There are no statutory qualifications for this – in principle you can appoint anyone for this. But in reality you can’t, as it would just make it the laughing stock. They have to appoint a respected senior Scottish lawyer.

“You can draw a Venn diagram of respected senior Scottish lawyers and of people who are prepared to say my principles are a lot worse than Richard Keen’s – and there will be no crossover.”

But Mitchell said it was inevitable that someone would be found, suggesting it would be a junior lawyer as he could not think of anyone who would be prepared to touch the “reputation ruining” post.

Another possibility he said would be the appointment of a Government minister to the role – such as Scottish Secretary Alister Jack.

He added: “It will just make the point they cannot get anybody of reputation who is prepared to take it on, which has got its own damage.

“What Richard Keen has done here – and I wouldn’t say I would have expected this of him – he has left them with a bomb on the table in the way he has done this and the terms of his letter.

“He was Tory Party chairman. I don’t find it at all surprising he has gone, but I would have expected him to go out very quietly.”

The UKIM Bill will go back to the House of Commons this week for another vote by MPs after passing its first reading.

Johnson – who claims the powers are needed to guard against the EU being able to “break up” the UK – has attempted to head off a looming rebellion by agreeing there will have to be a vote by MPs before they could be used.

Whether it is enough to ensure the legislation gets through unscathed has yet to be seen, with former Tory leader Michael Howard warning the Government “is still asking Parliament to break international law.”

There are likely to be further attempts to amend the legislation when it gets to the House of Lords.

Meanwhile, the Law Society of England and Wales has launched an urgent campaign calling for solicitors and members of the public to help “defend the rule of law”.

It said: “The rule of law is a founding principle of our country. It ensures that individuals, companies, and Government remain accountable to each other, and that fundamental rights are protected and enforced.

“The Internal Market Bill, in its current form, represents a direct challenge to the rule of law by including provisions which would allow for potential breaches of international law.”

The Law Society of Scotland has also issued a warning over the legislation, saying the rule of international law should be honoured.

“Adherence to the rule of law underpins our democracy and our society,” it stated. “We believe that to knowingly break with the UK’s reputation for following public international law could have far-reaching economic, legal and political consequences and should not be taken lightly.”