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's 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 today and will say: "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 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."
SNP treasury spokesman Stewart Hosie said Mr Brown is "unwittingly making the case for a Yes vote".
Mr Hosie said: "He had over a decade as chancellor and prime minister to deliver these new powers for the Scottish Parliament, and did none of them. Even worse, as prime minister Mr Brown actually blocked transferring control of Air Passenger Duty and other powers to the Scottish Parliament - even though this was specifically recommended by the Calman Commission.
"Gordon Brown's speech sounds as if he has no idea what is going on in the real world - the reality is that the welfare state is being dismantled by Westminster.
"George Osborne has announced £12 billion more welfare cuts, hitting the the most vulnerable people the hardest, and Labour are engaged in a Dutch auction with the Tories about who will cut the most.
"Scotland's finances are stronger than the UK's as a whole - we generate 9.9% of UK tax revenues but get just 9.3% of the spending, and therefore a smaller share of our national wealth is spent on welfare, which means that pensions and benefits are more affordable for Scotland.
"A majority of people in Scotland believe that decisions on tax and welfare should be taken in the Scottish Parliament, not Westminster - and the only way to achieve that is to vote Yes for an independent Scotland in September."