Plans for a supreme court for the UK could put Scots law and the devolution system at stake, according to a senior judge.
Lord Hope warned against uncertainty
Lord Hope of Craighead, Scotland's most senior Law Lord, said there were "crucial questions" over Prime Minister Tony Blair's reforms.
The move to create the supreme court was unveiled in this month's controversial cabinet reshuffle.
Lord Hope said there were fears that elements of Scots law could be subsumed by the English legal system, an outcome not permitted under the 1707 Act of Union.
He told the BBC's Politics Scotland programme that the new supreme court must be located, staffed and organised separately from the English courts to be legitimate.
There is a system for dealing with issues that arise and there is a very substantial question as to what its future is to be
The new body will handle cases from across the UK including final civil appeals from Scotland.
"There are two quite distinct things at stake," said Lord Hope.
"The first is the integrity of the Scottish legal system, which was protected by the Act of Union and has always been respected up until now.
"It may seem it's only a little bit of it that is at stake, but every bit matters.
"The second it the devolution system which is very recent - there is a system for dealing with issues that arise and there is a very substantial question as to what its future is to be."
The Law Lord is calling for "effective representation from Scotland" to ensure distinctive areas of Scots law and government are addressed.
Further details of the new system are expected in a consultation paper next month.
But Lord Hope said the idea must be "properly thought through" to avoid creating an "uncertain and untidy future" for Scottish justice.
"It has to be solidly based, properly thought through and constitutionally legitimate," he added.
BBC Scotland political correspondent Glenn Campbell said it was highly unusual for such a senior judge to speak out in this way.
"Whilst he's not campaigning in any way against the new supreme court, he's concerned that it has to be thought out fully before it's implemented and that it must take into account the Scottish interest," he said.
"Lord Hope wants to make absolutely sure that this thing is going to work."