Keir Starmer's blueprint for legally preventing Westminster from undermining Holyrood is the only way to do it constitutionally, the leading academic on Scottish devolution has insisted.

A dossier of options by Labour's last prime minister, Gordon Brown, has been formally accepted by the party, the Herald on Sunday understands.

It is believed the suite of policies will inform how an incoming government led by Sir Keir will reform the constitution.

The Herald on Sunday understands that Labour’s manifesto for next year’s general election could include plans that would legally prevent the UK Government from overriding Holyrood’s wishes in devolved matters as part of widespread constitutional proposals for the entire United Kingdom.

A leading devolution expert has stressed that a key proposal tabled for Labour to reform the House of Lords with a more representative second chamber that could “veto any attempt by the Commons to undermine devolution” is “probably the only way” to do so constitutionally.

Read more: SNP on the attack after Ian Murray rejects new powers for Holyrood

Meanwhile, another academic has warned against Labour taking a “gamble” that snatching the keys to Downing Street “will defuse the political potency of nationalism”, with a call to think long-term about strengthening devolution.

A Scottish Labour source said: " “Brown’s commission forms the basis of Labour’s thinking on how Labour will reform Britain’s constitution including resetting the relationship between Holyrood and Westminster, pushing power out and ending sticking plaster politics.”

But the UK Labour leader barely mentioned Scotland in his keynote speech to his party conference in Liverpool last week – other than praising the thumping Rutherglen and Hamilton West by-election victory and claiming that “old wounds of division exploited by the Tories and the SNP beginning to heal”.

The Herald: Keir Starmer at the Labour party conferenceKeir Starmer at the Labour party conference (Image: PA)

Instead, Sir Keir focused on boosting devolution in parts of England, stressing that “if we want to challenge the hoarding of potential in our economy then we must win the war against the hoarders in Westminster”, as he pledged to “give power back and put communities in control.”

But Sir Keir is yet to touch the vast majority of devolution proposals he tasked Mr Brown with drawing up.

One party insider told The Herald on Sunday that the UK Labour leader is “sitting on his hands” in offering the Scottish public a constitutional reason to vote for him.

They added: “Labour has been content with letting the Tories and the SNP scrap it out for political points on the constitution.

“It would be a huge mistake if some of Gordon’s proposals, many of which would help see off the rise of nationalism in Scotland, are never looked at properly.

“This could be our chance to end the argument that Scotland’s wishes are being ignored as part of the Union.”

Read more: Analysis: Labour risks taking Scotland for granted

But a senior Scottish Labour source suggested that the bulk of Mr Brown's recommendations could make up the constitutional offer to the public by the party ahead of next year's general election.  

Mr Brown joined Sir Keir and Scottish Labour leader Anas Sarwar in Edinburgh in December, as the trio set out the recommendations made by his Commission on the UKs Future, for an incoming Labour government to implement.

In his report, Mr Brown claimed that “many in Scotland share the dissatisfaction felt across each part of UK, including England, that decisions made by remote politicians and civil servants are holding back their communities and preventing them from getting the best out of Britain”, adding that “they are right to feel this way”.

He said: “Over the last decade devolved self-government has been undermined and bypassed by a government in London that has been able to ignore its democratic voice, most notably over Brexit and the UK internal market legislation passed despite the view of Holyrood.

“The cooperation which Scots are entitled to expect from their governments has all but broken down.”

The Herald: Former Labour prime minister Gordon BrownFormer Labour prime minister Gordon Brown (Image: PA)

The Scottish Government has consistently claimed that UK ministers have “undermined” devolution, particularly through the Internal Market Act – post-Brexit legislation that ensures a level playing field for business across all four nations of the United Kingdom.

But it has contributed to holding up the troubled deposit return scheme and could scupper a range of other devolved policies where the Scottish Government wishes to take a different path.

But a key overlooked proposal by Mr Brown, if rolled out by Labour, could protect devolved interests even when a UK government has a huge majority in the House of Commons to legislate as it pleases.

Mr Brown has suggested replacing the House of Lords with an elected assembly of nations and regions.

The last Labour PM’s plan would ensure “power is truly shared with the devolved legislatures and across England, and give voice explicitly to the different nations and regions of the United Kingdom”.

He added that the elected second chamber would allow “entrenchment and protection of devolved power”, adding that it would “ensure that the powers of the devolved administrations are always respected by central government, and cannot be overridden simply by a government using its majority in the House of Commons”.

Read more: Boosted Holyrood borrowing powers under Labour's devolution plans

Boris Johnson’s government repeatedly and with an apparent ease, ignored the Sewel convention that dictates legislation impacting devolved areas should only be passed with the support of devolved administrations.

But Mr Brown has called for “a new, statutory, formulation of the Sewel convention”, which would be “legally binding”.

He added that “the legislation giving effect to the Sewel convention should be one of the protected constitutional laws which require the consent not just of the House of Commons but of the reformed second chamber also”.

Mr Brown said: “This entrenches the convention as part of the UK's territorial constitution.

“It will succeed where the present legislation has failed in ensuring that the powers of the devolved legislatures cannot simply be overridden by the government of the day.”

James Mitchell, professor of public policy at Edinburgh University, has warned “we need to get out of the habit of assuming that adding to existing competences is an end in itself”, amid calls for an incoming Labour government to simply extend the devolved powers of the Scottish Parliament.

He added: “Accumulating competences as an end in itself has led to devolved government now having responsibilities for a wider range of matters, including taxation, but failing to pay sufficient attention to the consequences.

“We now have tax competences that mean spending on public services is now affected by the performance of the Scottish economy to an extent as never before.

"And this has resulted in Scotland losing a significant sum to spend on public services given the lack of focus from the Scottish Govt on the economy. So we need to be very careful what we wish for.”

He added: “Labour needs to think to the long-term and consider circumstances when a Tory Government returns to office in London and the conditions that have been conducive to an SNP advance – i.e. a Tory Westminster Government especially perceived as anti-Scottish – may return.

“Labour needs to consider how best to prevent or at least minimize this in future.

“The problem with the current UK system of government is that Scottish voices, and indeed those of Wales and many regions of England, can simply be ignored – the winner-takes-all system needs reform.

“At present – and it doesn’t matter whether SNP or Labour have most seats in Scotland so long as Tories have a Commons majority – Scottish majority opinion sits on the opposition benches and can be ignored.”

Professor Mitchell gave his support to the key principles in Mr Brown’s recommendations over the new second chamber and the legally-binding Sewel convention, backing “reforms that ensure that Scottish majority opinion cannot be ignored and existing devolved competences are protected”.

He added: “This is where, amongst other proposals, the complete overhaul of the Lords is vital.

“Making the second chamber an assembly or senate of nations and regions with the power to veto any attempt by the Commons to undermine devolution is an attractive proposition from a Scottish perspective.

“Getting rid of an elected chamber is in itself sensible but making it a territorial chamber is essential.

Read more: Angela Rayner rules out devolving employment law to Holyrood

“The proposal in the report to entrench devolved powers is imaginative and probably the only way given the maturity of the UK constitution.

“Drawing on provisions in the Parliament Act 1911 which retained the residual power to prevent extensions of Commons terms to any changes in devolution would entrench the devolved government’s powers without the agreement of the consent of the second chamber.”

Richard Parry from Edinburgh University’s Centre on Constitutional Change, said he was “surprised by the lack of engagement with Scotland” in Sir Keir’s speech in Liverpool.

He added: “He seemed to think that its job was to provide Labour MPs for Westminster. Sir Keir didn’t mention Gordon Brown’s report and it’s not clear whether or when he will respond to it in a way that would set out Labour’s general constitutional position.

“Eventually he will have to come up with some text for the UK and Scottish Labour manifestos.”

But he warned that “it’s hard for Labour to think constitutionally at the moment”, because “it requires some kind of conceptual structure to encompass diverse matters like Scotland, Wales, Northern Ireland, the upper house of parliament and the role of the courts”.

He said: “Of course there are, and always will be, reserved matters that might be devolved and often are in other systems.

“Employment law, broadcasting, equality law, air transport, driver and vehicle law, alcohol duties, research councils and international research collaboration, work permits and visa law – the list can go on.

“Brown was cautious about new powers in his report – and throughout his political career he has probably felt that the big economic matters should be done at UK level.

“Some small new devolved powers will likely be on offer from Labour, but it’s likely that they will be more comfortable than ever with their traditional position that it’s the economy, not the constitution, that matters and engages voters’ priorities.

“Their gamble is that for at least one UK election this will defuse the political potency of nationalism and they won’t need to be scared of the SNP.”