GORDON Brown is set to head a new UK-wide Constitutional Convention designed to reform and extend devolution and fend off Scottish independence.

The former Labour Prime Minister is understood to have agreed to chair the Labour initiative, which would draw heavily on citizens’ assemblies across the nations and regions.

The intention is to set up the Convention before next May’s Holyrood elections in order to counter SNP demands for a second independence referendum.

Although Labour-led, the Liberal Democrats have said they are interested in working with the Convention, calling it a "significant development".

Polls show the SNP on course for another overall majority in 2021, and Nicola Sturgeon has said she wants Indyref2 in the first half of the next parliamentary term.

Labour’s plan to save the Union is to ask voters to back greater devolution instead, with the ultimate goal a federal UK in which power would be shared more evenly around the country.

The Convention will also be pitched as way of addressing the frustration and lack of power felt by nations, regions and English mayors during the Covid crisis.

It would attempt to thrash out where powers should best lie and how to empower ordinary citizens.

However putting its recommendations into effect would rely on a future Labour government being elected at Westminster, with the next scheduled election not until 2024.

That would allow Ms Sturgeon to argue it would be too late and too uncertain an option next May.

The First Minister announced her own plan for a Constitutional Convention of politicians in January, but with the narrow aim of asserting Holyrood’s right to decide on Indyref2.

However it stalled because of Covid and a lack of cross-party interest.

Scottish Labour leader Richard Leonard said he would like the Convention to consider a “council of ministers”, in which the four nations would jointly agree big policy changes.

In an interview with the Herald, he said: “There needs to be work done through a Constitutional Convention.

“The Labour party needs to demonstrate to the people of Scotland that we are serious about this reform agenda and we want to get on with it.

“This is not something we are contemplating doing sometime down the line, it’s something that we are getting to work on straight away.

“In my view, the sooner that we can make progress on this, the better.”

Mr Brown and a host of English mayors yesterday wrote to Boris Johnson warning the UK is “in great danger” given multiple polls showing Scots “losing faith in the Union”.

They called for “a more federal Britain of nations and regions, a free and equal partnership with stronger devolution bringing power closer to the people, especially in England”.

They added: “Time is fast running out. We can still save our country but we need to act now.”

Scottish Liberal Democrat leader Willie Rennie said: “To have the heft of the former Prime Minister and Chancellor behind this important initiative to reform the United Kingdom is a significant development.

"The Liberal Democrats have long argued for reform to a federal United Kingdom so the nations and regions of the country can have a bigger say, and better ways of agreeing with each other and working together.

"We are keen to talk to Gordon Brown about the involvement of the Liberal Democrats as we want to use the knowledge and expertise we have developed over many years to make this initiative the success it needs to be.”

Labour’s Convention plan was supposed to be announced by UK leader Sir Keir Starmer in a speech tomorrow, but the event was cancelled because of Brexit developments.

Labour sources revealed Sir Keir would have unveiled the Convention, which he promised in his leadership campaign earlier this year as a way to “secure a new, decentralised UK”.

Crucially, the project would not rely on the UK Government’s approval, but get underway while Labour was in opposition, in readiness for power.

Mr Brown’s job would be as figurehead and chair of the Convention, the role filled by Canon Kenyon Wright in the Scottish Constitutional Convention which laid the groundwork for devolution and the Scottish Parliament in the late 1980s and 1990s.

In recent months, Mr Brown has been increasingly strident in calling for devolution reforms, saying the Coronavirus pandemic has exposed the over-centralised nature of the UK.

He told the New Statesman last month a Constitutional Convention could unite communities and examine matters “that directly affect our daily lives”, such as health, industry, jobs, social security, and climate change.

He said: “The virus has revealed some of the weaknesses that we’ve got to solve. The United Kingdom is a multinational country and we think of it only as a unitary state.

“It’s got diverse regions, as well as nations, yet we have thought too much in terms of centralisation.

“The sooner we recognise that this is a problem that’s got to be dealt with, the better. The danger is that the United Kingdom goes the way of the British Empire, and that is something that we have got to avoid by taking action now.”

Last weekend, more than 20 Labour peers organised by Lord George Foulkes also called for a review of the devolution settlement “by way of a UK Constitutional Convention”.

The peers said the Covid crisis had strained the union, and coordinated action was needed for the recovery.

They said: “We urge the Government to take urgent action to review the Constitution but, should it refuse to do so, we call on Keir Starmer, as Leader of the Opposition, to take such an initiative.”

SNP MP Kirsten Oswald, her party’s deputy leader in Westminster, said: “The Tories’ Brexit chaos is not a reason to postpone decisions on Scotland’s future – quite the opposite.

“No amount of constitutional tinkering of the kind proposed by Labour would protect Scotland from Brexit or a Tory power grab – only independence will do that.”

UK Labour’s 2019 election manifesto included a “renewal of parliament” by a UK-wide Constitutional Convention, led by a citizens’ assembly, to “answer crucial questions on how power is distributed in the UK today, how nations and regions can best relate to each other” and how to empower citizens.

The plan included abolition of the House of Lords in favour of an elected Senate of the Nations and Regions.