With a Scottish independence vote likely to shatter the United Kingdom after Brexit, a leading cross party group of United Kingdom politicians has put forward a federal UK solution in order to stave off an independent Scotland.

The outcome for Northern Ireland could well be an independent state with external links to the rest of the UK with some areas of commonality agreed upon.

Westminster would be effectively abolished and would feature instead a 146-member British parliament with an Upper House, becoming a chamber for delegates to the UK from the three different countries, Wales, Northern Ireland, and Scotland.

Scotland and Northern Ireland voted to stay in the European Union while England and Wales voted to leave. A major constitutional crisis has arisen as a result.

The Reform Committee led by former Conservative cabinet minister Lord Salisbury is to make the case for radical constitutional change in the UK, the Guardian newspaper has reported.

Members of the Constitution Reform Group include the former Liberal Democrat leader Sir Menzies Campbell, the former Labour Party secretary for Northern Ireland and for Wales Peter Hain, the former clerk of the House of Commons Lord Lisvane, and the former Ulster Unionist politician David Burnside.

The group also notes it has the support of former Conservative prime minister Sir John Major, and from the current chairman of the Conservative backbench 1922 Committee Graham Brad, all in an attempt to stop the United Kingdom disintegrating.

Read more: Enda Kenny under pressure to step down after major misjudgments

They are calling the new set up a voluntary union rather like the 50 states of America who all are part of the United States as well.

“A new governance of England, Scotland, Wales and Northern Ireland should be reinvented within a new voluntary union in a bid to save the UK from disintegration,” the document explains.

It proposes the existing union be replaced with fully devolved government in each country. Each country would be given full sovereignty over its own affairs.

The group says each country could voluntarily sign up for "shared UK functions which would include the monarchy as head of state, foreign affairs, defense, national security, immigration, international treaties, human rights, the supreme court, a single currency, a central bank function, financial services regulation, income and corporation tax powers, and the civil service." Countries could opt in or out on those categories.

The identity of the senior backers and John Major’s support are significant as the Conservative Party, now so dominant in England, has often been very reluctant to consider federalism.

The document's drafters are using the shorthand of “sovereignty maxed” to describe what each country will have.

“It would pull the rug from under independence,” said Lord Hain, while Salisbury stated his proposals would hand the initiative back to Scottish unionists.

The presence of David Burnside, a hardline Ulster Unionist, on the committee will certainly cause comment in Ireland's nationalist circles, which may welcome the plan as essentially breaking up the United Kingdom but who would vastly prefer Scotland to claim independence and do it that way.

Read more: Rathlin Island would join an independent Scotland to remain in EU