A new supreme court would take over appeal duties from the Lords

And the move could be unconstitutional if the new court is seen to be part of the England and Wales court system, it was argued.

The claim came from the Faculty of Advocates, representing Scotland's 465 practising advocates, in its formal response to the White Paper which proposes the change.

The new supreme court would replace the appeal court functions of the House of Lords.

The Lords at present acts as the ultimate court of appeal for Scotland in civil cases, and the onset of devolution and human rights legislation means the Lords could also handle some future criminal appeals.

The faculty said it had "serious concern" that the supreme court plan, as drafted, fails to respect the independence of Scots law under the 1707 Act of Union.

'UK-wide role'

Any court with jurisdiction in Scotland cannot be a part of the England and Wales court system and the faculty warned: "The constitutional significance of this cannot be overstated.

"Any attempt to create a supreme court which did not comply with these requirements would be contrary to the constitution of the United Kingdom and any purported act in, or affecting, Scotland in such a court would be unlawful and of no effect in Scotland."

The faculty's concern stems from the proposal that the supreme court be administered and funded by the Department for Constitutional Affairs.

Advocates are concerned a new court could threaten Scots law

It suggests instead that there should be a separate "Supreme Court Service" funded by a Westminster block grant, and answerable only to the supreme court.

"Given that the Department for Constitutional Affairs is responsible for the administration of the court service in England and Wales, but not in Scotland, were that department to be responsible for the administration of the Supreme Court, that would give the appearance that the supreme court was part of the courts of England and Wales," said the faculty.

It goes on to argue that the new court be based in premises which are not used by the courts of England and Wales, and possibly at a location away from London, like a city in the north of England, or Cardiff or Belfast, in order to emphasise its UK-wide role.

The faculty also suggests that at least three full-time supreme court judges have expertise in Scots law, in order to ensure that Scottish appeals are heard by a bench with a majority of Scots-trained lawyers.