Constitutional reforms should be made to create a “union for social justice” in which the UK can pool and share resources for the benefit of all, according to former prime minister Gordon Brown.
Mr Brown says Scotland will be strengthened by his proposed constitutional changes while remaining within the union.
The Kirkcaldy and Cowdenbeath MP wants the Scottish Parliament to be made irreversible, with “maximum devolution of powers in training, transport, health, the Crown Estates Commission and the running of elections”.
He has also proposed UK legislation to state the shared purpose of the union, “namely the pooling and sharing of resources for social justice”.
Mr Brown will publish more details of his proposals next month, which he believes present a more attractive vision for Scots than independence.
His comments come as Labour’s devolution commission continues to consult on its findings, with final recommendations to be decided in time for the independence referendum.
The former PM is due to give a speech on Scotland’s future in his constituency on Saturday.
He is expected to say: “I support the excellent work of Alastair Darling and the Better Together campaign.
“One of the keys to the next stage in the constitutional debate will be in the recommendations of Labour’s devolution commission.
“I am of the view that the party that first created a powerful Scottish Parliament is best-placed to strengthen devolution and to create a stronger Scottish Parliament in a stronger UK.
“We can show how with our reforms, to be implemented by Labour administrations in Westminster and in Edinburgh, we can address some of the greatest social and economic challenges a future Scotland faces.”
Mr Brown will also attack the SNP over funding for their plans for an independent Scotland.
He will say: “First, they calculate oil and gas revenues as at least £6.8 billion in 2016-2017 when all formal and independent forecasts suggest the correct figure is likely to be around £3.5 billion, leaving a £3.3 billion shortfall. To make this up requires a rise in income tax of 10p.
“Second, they have failed to calculate the cost of European Union membership without the British rebate, which Scotland would not benefit from.
“In consequence, Scotland’s net membership costs could be as high as £500 million that the SNP have not budgeted for. Scotland may even have to contribute to the remaining UK rebate like all other member states.
“Third, while the SNP have a working party on the ‘affordability’ of pensions, Scotland receives proportionately more spending on pensioners than the rest of the UK and more in incapacity benefit.
“With the rising number of pensioners in future years, Scotland will receive an even greater dividend from its membership of the United Kingdom.”
He will add: “It is time to set out with more detail the positive, principled and forward-looking arguments for a strong Scottish Parliament in a strong UK.
“It is right to set out a Labour vision of the future: the alternative to separation that shows how enhanced devolution within the union offers the Scottish people a fairer deal and a better dividend.”