Suddenly, it seems, everyone and her dog is in favour of giving the cities and regions of England more control of their own affairs. Think tanks are calling for it; Nick Clegg has backed it; and, with the Holyrood parliament set to see its powers beefed up even if Scotland votes “No” in this week’s referendum, the pressure to balance this with devolution south of the border will be enormous.

The problem is, though, that it’s extremely tricky to come up with a model for devolution in England that doesn’t look a bit, well, silly. Here’s why.

1) England is really, really big.

Far bigger than the rest of the country, in fact. At the time of the 2011 census, England contained around 85 per cent of the UK population. To give you a sense of quite how small a share of the UK population the three Celtic countries contain, there are almost as many people in London as there are in Scotland, Wales and Northern Ireland put together. (Include the wider metropolitan region, and there may actually be more.)

All this means that the idea of creating a separate English parliament is a bit of a non-starter: it’d just replicate the existing House of Commons.

An alternative would be to keep the House of Commons, but ban non-English MPs from voting on English matters. But that, too, throws up problems. Specifically:

a) You have to define what “English matters” are, which is surprisingly hard (is a Budget?); and

b) There’s a risk that a UK government will find it can’t command a majority of the House of Commons for the huge swathe of its manifesto which only applies to England, creating deadlock.

So, despite support for the idea from Tory rightwingers like John Redwood, that may be out too.

2) No one likes the regions.

Here’s another way of illustrating quite how big England is. Of the country’s nine official regions (the North East, South West, etc.), five of them are bigger than Scotland; eight of them are bigger than Wales; all of them are bigger than Northern Ireland.

So, for a while, the last government’s favoured solution to the devolution problem was regional parliaments, each of which would represent a similar number of people to devolved parliaments in Wales, Northern Ireland and Scotland. It got as far as holding a referendum on creating an elected assembly for the region it felt had the strongest regional identity. Here was the result:

Which kind of killed that idea.

The vote resulted in part from an anti-government mood in the wake of the Iraq War. But it also highlighted the fact that – unlike US states or German Lander – most of the English regions have no historic identity that drives them to want their own political representation. And their boundaries repeatedly throw up anomalies. The red dot on this map (right) is the commuter town of Swindon which, being part of Wiltshire, finds itself lumped into the South West region – despite the fact it has less in common with Cornwall than with nearby Reading. By the same token, two-thirds of the London commuter belt is in an L-shaped South East region; the rest finds itself lumped in with rural Norfolk.

So – regional parliaments seem to be out, too.

3) Local authorities are the best option. But they’re still not a very good one.

The most likely contender for a lower tier of English government, then, would be its cities, which are increasingly seen as the drivers of economic growth. The Greater London Authority is seen as pretty successful; but the next tier of cities (Birmingham, Manchester, Leeds, etc,) haven’t had area-wide elected bodies since the metropolitan counties were scrapped in the mid-80s.

To that end, the UK is currently in the middle of creating a series of “combined authorities”: units in which groups of councils covering entire city regions pool their powers to work together on things like transport and infrastructure.

But you won’t be surprised to learn that these, too, bring problems. One is accountability. These bodies are currently unelected, with the uncomfortable result that the Newcastle-based one covers exactly the area that the regional assembly would have done, with the slight difference that nobody is voting for it.

For another, there have been a string of frankly hilarious rows about what to call them. One combined authority combines the five boroughs of the old metropolitan Merseyside with neighbouring Halton. It’s very obviously a sort of greater Liverpool, but representatives from some of the smaller boroughs resisted the idea of acknowledging this fact, for fear of being trampled on by their bigger (and, let’s be honest, more important) neighbour. So for a while the region was stuck with the catchy name of the “Halton, Knowsley, Liverpool, St Helens, Sefton and Wirral Combined Authority”. This lunacy was only brought to an end when Liverpool threatened to walk.

The biggest problem with using city regions as the basis of devolution, though, is that they are incomplete. The combined authorities cover the areas surrounding Manchester, Liverpool, Sheffield, Newcastle and Leeds. There’s talk of another to cover Birmingham, too. But that still leaves huge swathes of the country for which there is no obvious authority to devolve power to.

The IPPR’s answer, proposed in a report published late last week, is to beef up existing local councils, giving them more power over their own finances, economic development and local public services. The think tank’s plan for a “10 year programme of decentralisation” would also include legislation to protect the constitutional status of local authorities (to ensure future governments can’t simply abolish them for political reasons). And it would mean establishing “county combined authorities”, to plug the gaps between metropolitan regions.

Any such administrative change, though, would be bottom-up, with areas invited to bid to become combined authorities at the start of each parliament. It’s not clear whether, given the current anti-politics mood, there’d be an appetite to do any such thing.

The alternative would be for a government to impose the system, rather than wait for bids to come in. If that happened, then the EU’s sexily named NUTS 2 statistical regions might make a good starting point. They’re not perfect, but they get us round the radical differences in county population size, and the silliness of treating Watford and Cromer as if they have anything in common beyond being vaguely north of London.

Of course, this would still leave us in a ridiculous situation in which the Scottish parliament and Welsh assembly are effectively placed on a par with Essex county council, which, last time we checked, did not have its own legislative powers. This may not be enough to stave off concerns about the growing imbalances in the British constitution.

Map credits: edited images from Wikimedia Commons.