Gordon Brown, who is widely credited with saving the pro-Union campaign in the 2014 Scottish independencereferendum, will today set out a 'third option' for Scotland's future, based on more powers being transferred to Holyrood after Brexit.
The former Labour prime minister will suggest that the Scottish government should be given the power to set VAT rates and sign international treaties.
Brown, who argued for 'devolution max' in 2014 and since, will say in a speech that control over agriculture, fisheries and environmental regulation could be transferred.
His intervention comes after a speech by Theresa May yesterday pledging to preserve the 'precious, precious Union' and as Nicola Sturgeon, the SNP leader addresses her party's Spring conference.
The first minister set out her position five days ago, saying a fresh vote was necessary in the wake of Brexit.
She will tell the SNP conference that the will of the Scottish Parliament 'must and will prevail' over the issue.
Brown, who is seen as one of the few former Westminster politicians with credibility north of the border, will address the Festival of Ideas, in Kirkcaldy, Fife, where he will call for the repatriation to Scotland of £800m spent by the EU.
Further, he will propose that the Bank of England becomes the Bank of England, Scotland, Wales and Northern Ireland, with fully staffed representation in Scotland, 'to reinforce the fact that the pound is for everyone'.
Brown was the main architect of the 'Vow', a cross-party promise of more powers for Holyrood, which many believe boosted the No vote ahead of the Scottish independence referendum in September 2014.
Brown will argue a new form of federal home rule is needed to unite the country and avoid years of 'bitter division'.
'The third option, a patriotic Scottish way and free from the absolutism of the SNP and the do-nothing-ism of the Tories, is now essential because post-Brexit realities make the status quo redundant and require us to break with the past,' he is expected to say.
'The status quo has been overtaken by events because unless powers now with the European Union are repatriated from Brussels to the Scottish Parliament, the Welsh Assembly and the regions, Whitehall will have perpetrated one of the biggest power grabs by further centralising power. employment and energy.
'The patriotic way means that Scotland is not caught between a die-hard conservatism that denies the Scottish Parliament the powers it needs and a hard-line nationalism that throws away the resources we secure from being part of the Union.'