With the SNP citing Coalition welfare cuts as evidence of how the Union imposes callous policies on Scotland, the former Labour prime minister tried to wrest the fairness agenda away from the Nationalists with a speech in Fife.
Speaking in Lochgelly as part of Labour's campaign in the Cowdenbeath by-election, Brown said greater powers for Holyrood could be used to forge a "union for social justice", in which Scotland benefited from the pooling of resources across the UK.
However, the SNP said the Kirkcaldy and Cowdenbeath MP was "unwittingly making the case for a Yes vote" because he had failed to devolve new powers when he had the chance while in office.
SNP Treasury spokesman Stewart Hosie MP said: "Gordon Brown's speech sounds as if he has no idea what is going on in the real world … George Osborne has announced £12bn more welfare cuts … and Labour are engaged in a Dutch auction with the Tories about who will cut the most."
Scottish Labour's commission on devolution, which last year suggested devolving income tax, is due to deliver its final report in March. In a possible trail of its work, Brown called for the Scottish Parliament to be made irreversible - Westminster retains the power to abolish it - and said there should be "maximum devolution of powers" in transport, health, the Crown Estates Commission and the running of elections.
He said: "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."