Murdo Fraser has always been one of the most radical and interesting thinkers in the Scottish Conservative Party and he should prove it again today with a speech in Glasgow in which he will set out a vision of Scotland as part of a federal United Kingdom.

Mr Fraser, who was defeated by Ruth Davidson in the leadership election in 2011, is proposing autonomous, devolved administrations for Scotland, Northern Ireland, Wales and England; under his plan, there would also be reduced representation in the Commons and, at the top of the structure, there would be a US-style senate.

For the Conservatives, who supported a No vote in the 1997 referendum, it is a radical idea, although Mr Fraser has always been among the most friendly in his party towards devolution. His plans also reflect the direction of travel in Scottish, and UK, politics. The Liberal Democrats have long been fans of federalism but Labour, too, are looking at including plans for a senate in their manifesto for the General Election. Ed Miliband is also considering handing greater control over economic development and other matters to the UK's biggest cities. It means senior figures in all of the three pro-Union parties are talking about federalism or something very like it.

This is a most welcome development in the debate around the independence referendum and what happens to the UK in the event of a No vote. Some of the talk of devolving more power to cities is an attempt to rebalance the overpowering economic effect of London but the new consensus emerging around further devolution is also recognition of the fact that piecemeal reform of the UK's constitutional structure is no longer acceptable. It has led to all kinds of imbalances, not least the West Lothian question. What is more, the flaws in the system would only become greater if there were a No vote and more powers were devolved.

A more coherent way forward is needed as well as a solution around which supporters of all parties can unite, especially those who want many more powers for the Scottish Parliament but do not want independence. The pro-Union parties have already responded to this desire with a promise of more powers for Holyrood but there remain significant differences between them. The Tories, for example, would like Scotland to be given full income tax powers; Labour would prefer to hand MSPs the power to increase the higher rates of income tax but not lower them.

Depending on which, if any, of these plans go ahead, they could make the constitutional imbalances worse and it may be that only a UK-wide restructuring along the lines proposed by Mr Fraser will sort it out. The Strathclyde Commission, set up by the Tories to look at devolution, hinted at such a restructuring but did not make specific recommendations. Mr Fraser is the first senior Tory to talk openly about the idea and it is to be hoped others will join the debate. As Donald Dewar said, devolution is not an event but a process and the aim of that process should be to find a new, democratic constitutional settlement that can win popular support across the UK.