Gordon Brown is calling for the House of Lords to be replaced by an elected senate and for more powers for the Scottish Parliament after the Brexit vote.
In a move immediately attacked by the Scottish Nationalists, he says the decision to leave the EU means the UK needs to rethink its constitutional structures.
The former Prime Minister says his proposals would bring the UK much closer to a federal system, and weaken the case for a fresh Scottish independence referendum.
First Minister Nicola Sturgeon has already begun preparing for a second independence referendum after Scotland voted to remain in the EU in the UK-wide vote on Europe on 23 June.
In a speech at the Edinburgh book festival, Mr Brown said the Scottish Parliament should now be given powers currently controlled by the EU, such as fisheries, agriculture and social rights.
He called for a UK-wide constitutional convention to investigate his proposed changes, which include a UK senate for the nations of the UK and the English regions.
“We enter autumn with two entrenched positions which are polar opposites,” Mr Brown said.
“The UK government wants Scotland in Britain but not in Europe and the Scottish government wants Scotland in Europe but not in Britain.
“Now is the time for fresh thinking and not a replay of the tired old arguments and slogans.
“I believe that we should examine a way forward that offers a more innovative constitutional settlement, more federal in its relationship with the UK than devolution or independence and more akin to home rule than separation.”
In a move that could provoke a clash with English Labour MPs, Mr Brown estimates his proposed overhaul would mean the Treasury sending up to £750m more to Holyrood, to cover agricultural subsidies, academic grants and regional funds now provided by the EU.
During the Scottish independence referendum, Mr Brown negotiated with then-Prime Minister David Cameron to sign a joint pledge with rival party leaders to deliver further devolution.
It became known as the Vow.
But SNP MSP James Dornan said the former Prime Minister’s latest comments were “an astonishing development”, claiming: “The architect of ‘the Vow’ now says that the powers it delivered don’t go nearly far enough.
“This is an astonishing development that shows how the very real threat of Scotland being dragged out of the EU against our will is causing people to fundamentally rethink firmly held views on the constitution.
“We agree that doing nothing is not an option but the suggestion of a federal UK is very unlikely to win support across England.
“Keeping Scotland in Europe is the Scottish Government’s starting point – and the First Minister is absolutely right to keep all options on the table to achieve that, including a second independence referendum.”
Source: Sky News