It’s obvious why the Prime Minister and the other party leaders have issued their latest offer to Scotland, a couple of days before the referendum. More interesting is whether, if Scots do vote No, it will prove sustainable – or acceptable to England.

The new pitch rests on three central pillars:

  • New powers for the Scottish Parliament
  • “Equitable” sharing of UK resources (aka public spending)
  • Continuation of the Barnett Formula, by which taxpayers’ money is transferred from England to Scotland (and Wales and Northern Ireland)

In effect, this is a proposed update of the devolution settlement forged by Tony Blair and Gordon Brown in the late 1990s – maintaining the current funding structure, extending the process of devolving powers to Scotland and – crucially – taking no action to address the democratic deficit in England, whose laws are still voted on by MPs from Scotland, Wales and Northern Ireland.

Therein lies the first problem. The Blair devolution settlement has failed. It intended to sate Scottish nationalism, which instead has prospered in Holyrood. It claimed to foster democratic responsibility north of the border, but simultaneously continued a subsidy stream which allowed the Scottish government to gild its abilities with English taxpayers’ money. It was supposed to establish a better balance among the Home Nations, but totally neglected England – the only time they thought of us was Prescott’s shoddy 2004 bid to carve us into artificial regions, which suffered the fate it deserved at the hands of the North East’s voters

In short, the current crisis facing the Union was borne out of the imbalanced, misconceived fudge which Blair and Brown established. Simply tacking new powers onto that structure isn’t viable and guarantees a new crisis further down the line, even if it persuades enough Scottish voters to plump for No on Thursday.

Of course, it may never come to fruition. If the plan survives in the short term (by a No vote) it may still be killed off in the medium term – I severely doubt that English MPs, particularly Tory MPs, or English voters will accept the proposal.

England cannot justly be left out of yet another rewriting of our Union. While few would object to more powers being devolved to Holyrood, the relationship must not simply be one of give, give, give. Financially and democratically the English currently lose out – and the new plan would only accentuate that unfairness.

If Scotland wants a greater degree of freedom, as is its right, then that means cutting some of the apron strings, too. The Barnett Formula should end, as should the ability of Scottish MPs to vote on England-only laws at Westminster. Barnett (who didn’t actually invent the Formula, and is intensely embarrassed of its survival) never intended the financial deal to last for more than a couple of years, while the current voting arrangement flies in the face of everything devolution is meant to be about.

In a federal UK, as proposed in the ConservativeHome Manifesto, all the Home Nations should have the equality of Devo Max. As in any federal system, there would still be some fiscal redistribution, but it would be targeted where it was needed, not where it was politically convenient – the injustice of wealthy Scottish students getting free university education while enjoying higher public spending per capita than the poor of North East England would be ended.

Cameron, Clegg and Miliband haven’t included this in their new offer for the future of the Union – but they may well be forced to. The old, failed settlement was established without the full involvement of the whole UK – people seem less willing to have their money spent, or vote limited, without their permission again. Labour MPs are predictably wary of removing their party’s in-built advantage in Westminster, but some Conservatives are already speaking out publicly on the need to consider England.

Others are privately unhappy, and if UKIP try to capitalise on the issue – as I fully expect them to – then more marginal MPs may start to speak out, too.

Even if some way is found to push through a new deal for Scotland without considering the rest of the Union, though, how long will it last? Westminster has tried to implement an unbalanced devolution before – and all it brought us was the current sorry state of affairs.