There is no democratic country in the world whose main lawmaking body is made up of a first and second class of elected representatives. And there is no state in the world, federal or otherwise, in which one part of the country pays national income tax while the other part is exempt. Yet these are the two principal constitutional proposals that have come from the Conservative party in its kneejerk response to Ukip’s English nationalism and an ill-thought-out drive to impose what is commonly called “English votes for English laws” (Evel).

Under their plans, “the mother of parliaments”, once lauded as a beacon for fairness and equality before the law, would become home to the first elected body in the world to decree one of its constituent parts – Scotland – half in, half out of its lawmaking process. Second-class status for Welsh and Northern Irish representatives might soon follow.

But this is not simply a Westminster insiders’ issue, relevant only to the sensitivities of MPs; it is about the status of each nation in what has hitherto been one United Kingdom. By according a first-class status to England within Westminster and a second-class status to the rest, the constitution would be changed for ever. And the government of the day would become a servant of two masters, with its ability to govern depending one day on the votes of the whole of the UK and the next day on English votes only.

Taken alongside the Conservative proposal to devolve all income tax decisions to the Scottish parliament, Scottish MPs would find themselves excluded not just from ordinary English lawmaking but from some of the most controversial and sensitive decisions a parliament can make – on income tax and the budget.

Chaos would follow: for, once Scotland and then Wales and Ireland became exempt from contributing to UK income tax – but still benefiting from it through Barnett formula allocations – English consent for pooling and sharing across the UK would quickly dissipate. Whether by malice or by mistake, the Conservatives would have done the Scottish nationalists’ job for them.

If you had wanted to kill off the UK, you could not have devised a more lethal way. “A nation divided against itself cannot stand,” Lincoln famously said, quoting Mark’s Gospel. He could have added the rest of that text: “Every kingdom divided against itself is brought to desolation.”

The starting gun for this developing constitutional crisis was fired the morning after the Scottish independence referendum, with the prime minister’s announcement of Evel. When carefully analysed, his was not a proposal for greater English rights but for fewer Scottish rights. Everything that has been said since that fateful morning has confirmed that the central Tory proposition is the reduction of Scots’ voting rights in the Commons – an issue material to the referendum that should have been announced before, rather than after, the vote. The failure to do so has fuelled the demonstrations, petitions and allegations of betrayal, bad faith and breach of promise, which have dominated the Scottish debate ever since.

What can end this constitutional impasse? It requires us to recognise that the fundamental problem of our UK constitution is not that English MPs can’t vote on Scottish issues – that is merely a symptom of the problem – but a basic imbalance in the size of the four nations. England is 84% of the union, Scotland 8%, Wales 5% and Northern Ireland 3%. When translated into representation at Westminster, the 533 English MPs can, at any time they choose, easily outvote the 117 parliamentarians from the rest of the UK.

Recognising this permanent dominance in numbers, every generation has had to find a way to balance the power of the majority nation to impose its will with some protection for the minority nations. This is not a problem unique to Britain. The US, Australia and many other countries have had to find ways of managing the gross inequalities in the size of their constituent parts. Their constitutional protections for minorities show that a blanket uniformity of provision – such as Evel mimicking Scottish votes for Scottish laws – does not ensure fairness of treatment.

So, as the price for keeping the American union together, California accepts that it has just two members of the US Senate to represent its 38 million citizens, the same as Wyoming has to represent its 583,000 people. Similarly, the price New South Wales pays for Australian unity is one senator for every 580,000 people, in contrast to Tasmania’s one senator for every 40,000.

And nor is fair treatment for minorities in the Spanish senate, the Swiss council of states, the South African national council of provinces, and the Brazilian, Nigerian and Mexican senates achieved by the crude uniformity of the Evel approach, but through special arrangements that recognise minority needs in their states or provinces.

So there is a way forward that can keep the UK together, one that recognises the sizes of each nation and region and is founded on both a sensitivity to minorities and self-restraint by the majority. It involves retaining income tax as a shared tax, and ensuring the Scottish parliament is accountable for the majority of its spending. But it could also involve changes in Commons committee procedures that would recognise an English voice on English issues without undermining the equal status of MPs – while enthusiastically supporting more powers for Wales, Northern Ireland and forms of devolution that meet the distinctive needs of English cities, counties and regions.

No longer should we see Britain as a centralised, unitary state founded on an undiluted Westminster sovereignty, but as a diverse partnership of nations, cities and regions that pool and share risk, rewards and resources as part of one United Kingdom. Ironically, under the logic of the Conservative proposals, London MPs could be excluded from voting on matters devolved to the London assembly. But there is a bigger truth: that the most powerful part of England – London – has secured the greatest devolution of decision-making in England. It is time we supported greater devolution to empower England’s other great cities and regions.

By embracing every nation and region, and every interested civic group, in a 2015 constitutional convention, the voice of England would be heard – and not in angry opposition to the voices of Scotland, Wales and Northern Ireland, but alongside them.