A former Scottish Labour adviser has called on Anas Sarwar’s party and the Lib Dems to form a “progressive alliance” to remove the SNP from power at Holyrood.

Andrew Liddle, who worked with ex-party leaders Kezia Dugdale and Richard Leonard, called on the parties to put aside “pride and personal ambition” for the “greater good”.

It came as Scottish Lib Dem leadership candidate Alex Cole-Hamilton signalled he would be willing to enter a future Holyrood coalition with Labour.

The Lib Dems and Labour ran the Scottish Executive in the first two terms of the Parliament, but their support base has crumbled in the fourteen years since the SNP swept to power in 2007.

But a growing number of voices are calling for the two pro-UK parties to work closer together in a bid to replace the SNP atfter the next election.

Outgoing Scots Lib Dem leader Willie Rennie said cooperating with Labour on “issues of common interest would be a good thing”.

In an article for the Daily Record published below, Liddle - an author and former Scottish Labour spin doctor - said an “anti-nationalist and progressive” alliance would be a “real alternative”.

He suggested a “non-aggression pact” might “serve both parties well”.

Liddle concluded: “The inescapable fact is this: we have done it before, and it worked. So why not do it again?"

Launching his Lib Dem leadership bid in an Edinburgh cafe yesterday, Cole-Hamilton reached out to Sarwar: “If we are to see a change in Government from the SNP, who have stagnated for 14 years in power, then we need to seek out a progressive alternative. And that might be a coalition with Labour.”

An SNP spokesperson said: “There is absolutely nothing progressive about standing in alliance with Boris Johnson to deny the democratic will of the Scottish people to choose our own future, free from the vindictive and inhumane policies of consecutive Tory Governments.”

Willie Rennie has plenty to be proud of during his decade as leader of the Scottish Liberal Democrats, but his greatest legacy could be his last act - forging a real progressive alliance with Scottish Labour.

As he rightly pointed out in his final days as leader, middle Scotland deserves better than the sham social democracy of the SNP and the bullish flag waving of the Tories, which so often degrades itself and the Union it claims to serve by acting as a mere apologist for English nationalism. In that toxic mix, an alliance between Labour and the Liberal Democrats – anti-nationalist and progressive – would be a real alternative.

What exact form this cooperation would take is up to Scottish Labour leader Anas Sarwar and Rennie’s inevitable successor, Alex Cole-Hamilton. A non-aggression pact, for instance, might serve both parties well. Certainly, the precedent for a close working relationship is strong. It is the Labour Party and the Liberal Democrats, working together, who created the modern, progressive Scotland that the SNP like to claim credit for. Policies and issues such as free personal care, greater LGBT rights and a focus on tackling poverty were all championed by the Labour-Liberal Democrat administration.

But a Lib-Lab alliance would not only share a common legacy – it would also share a common vision for the future. Both parties share an opposition to a second independence referendum and independence, correctly arguing that more can be achieved together than apart. Both rightly oppose the calamity of Brexit, and appropriately cite it as one of the best cases against – rather than for – independence. But both parties are also dissatisfied with the status quo.

They share an aspiration to create a more federal UK that would enhance devolution while strengthening the bonds of the Union. While this concept has been much discussed, it has yet to take a firm form. A clear vision developed and advocated by both parties is likely to be better conceived and better supported than one that is created by one party alone.

Ultimately, an alliance could help reinvigorate the two parties that have suffered the most from the constitutional division of the last decade. Both parties have tried and failed to change the game, but they could change the players. By providing a blueprint for Sir Keir Starmer and Sir Ed Davey, it could also help renew the cause of progress across the UK.

Of course, the naysayers and juveniles on both sides will cry foul of greater cooperation. The Labour left will wax lyrical about tuition fees, the Liberal Democrat dissenters, the Iraq war. Pride and personal ambition – those great enemies of progressive politics – will have to be put to one side in favour of the greater good. But the inescapable fact is this: we have done it before, and it worked. So why not do it again?

Andrew Liddle is a former Scottish Labour adviser. He is currently writing an account of Winston Churchill’s 14 years as MP for Dundee, to be published next year.