SECTION 35 of the Scotland Act “has to go” if a UK Labour government is serious about constitutional change, the Deputy First Minister has said.

John Swinney told The National that proposals put forward by Keir Starmer’s party to embed the Sewel Convention – which says Westminster will not normally legislate in devolved areas without Holyrood’s consent – into law would not go far enough as long as Section 35 exists.

The controversial clause in the Scotland Act gives the Scottish Secretary the power to unilaterally block bills passed by the Scottish Parliament if they have “reasonable grounds” to think the law may adversely affect reserved areas.

The Tories’ Scottish Secretary, Alister Jack, used the power for the first time in January to prevent Scotland’s Gender Recognition Reform Bill from becoming law.

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Swinney told The National: “What the use of the Section 35 power demonstrates is that the UK Government has got the power to veto the conclusions of the Scottish Parliament.

“Now, if you add that to the series of decisions that have now been taken to ignore the Sewel Convention … that wasn't breached for 19 years and has now been breached about seven or eight times.

“I think what those two examples tell you is that there is a sustained approach being taken by this current United Kingdom government to undermine the Scottish Parliament and its legislative competence and its level of responsibility. And people in Scotland need to consider that very carefully.”

He went on: “Obviously, what this whole debacle demonstrates is that Section 35 is a means of essentially overturning the legislative powers of the Scottish Parliament. So you have to have a protection against that.

“That essentially means that Section 35 has to go, because for as long as that power exists, then whatever you do to the Sewel Convention there's Section 35 that can trump it.

“So, as usual with the Labour Party it’s a kind of incomplete solution.”

The National: Alison Thewliss MP

Alison Thewliss (above), the SNP’s home affairs spokesperson at Westminster, also said that Labour would need to take action beyond embedding the Sewel Convention in law to show it is serious about constitutional reform.

The Glasgow Central MP told The National: “Labour have promised an awful lot before ... Gordon Brown has essentially been making the same speech now for a decade about how things need to change. The Labour Party promised the abolition of the Lords 110 years ago, and we're still waiting for that to happen.

“If they came through on any of these plans, then that's certainly helpful compared to where we are just now, but they also have to go and reverse all of the things that the Tories have put in place.

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“Things like the Internal Market Bill, what are Labour going to say about that? Are they going to revoke the Internal Market Bill? If they don’t do that Westminster will still retain the powers to overrule the will of the Scottish Parliament whenever it chooses to and on whatever issue it chooses to.

“So I want to hear from Labour what they're going to do about those pieces of legislation which infringe upon Scottish rights. Likewise, the trade union bill that went through on Monday will Labour repeal that?”

The two top SNP figures’ comments come after Stephen Noon, the former chief strategist of the Yes campaign, said the SNP should get on board with Labour’s plans to reform the UK constitution.

Noon argued that giving Scotland real consent, rather than one based purely on convention, was “likely” to be one of the first laws introduced by a UK Government under Starmer.

Noon suggested that the Scottish Parliament could offer to consent to Labour’s plans for constitutional change on the condition of Holyrood being given additional powers, “for example, gaining more job-creating powers or, indeed, securing the power for Holyrood to legislate for an independence referendum”.

He said Starmer ignoring such a proposition would “go against the very grain of the changes he is looking to introduce”.