Media playback is unsupported on your device Media caption The UK government's publication is the first in a series of papers supporting the Union

An independent Scotland would be seen as a separate state under international law, legal opinion published by UK ministers has said.

The comments came as the Westminster government released the first in a series of papers on the issue.

UK ministers also said Scottish devolution had established itself as a trusted form of government that would be lost under independence.

The Scottish government is staging its independence referendum in autumn 2014.

SNP ministers said it would be "staggeringly arrogant" of the UK government to suggest that, under independence, Scotland would be left with nothing.

Scottish Secretary Michael Moore outlined the UK argument along with Advocate General Lord Wallace - a former Scottish deputy first minister - and Scotland Office minister David Mundell.

What we've learned today from the working group of economists, asked by the Scottish government to draw up a blueprint for power, is that credibility and stability will require Scots to do an elaborate deal with London

It included legal opinion from Prof James Crawford of Cambridge University and Prof Alan Boyle of Edinburgh University, that Scotland would become a new state after independence.

They said the remainder of the UK would be considered the "continuing state" under international law.

Speaking in Edinburgh, Mr Moore said: "No matter which side of the debate you are on, we all recognise this will be a momentous choice.

"It's a choice that is too important to get wrong and a choice that we must make on the basis of evidence, not assertion.

"To do that, we all need to be able to consider the facts."

The Scottish secretary said devolution had allowed Scotland to make key decisions in areas like schools, policing and the health service.

He added: "Unless we understand what we have - how our nation contributes to and benefits from being part of our United Kingdom, we cannot begin to consider the implications of independence.

Analysis It is in the nature of legal opinions that they are rarely black and white. And so it is with the UK government's new advice on Scottish independence. Profs James Crawford and Alan Boyle clearly think it is "most likely" that independence would create only one new state - Scotland. They expect the rest of the UK would just carry on, having inherited the current UK's treaties and memberships of international organisations. Scotland, they argue, would have to negotiate its way in the world from scratch, including joining the EU as a new member. However these eminent lawyers do not completely discount other possibilities. In the case of the EU, they say automatic membership is "not inconceivable" if member states were "willing to adjust the usual requirements" in Scotland's circumstances. They also note the "importance of negotiations in predetermining the consequences of independence". In other words, if the UK and Scottish governments wanted to agree a Czechoslovak style "velvet divorce" creating two new, equal successor states, they could do so. Of course, the UK government does not want to run a new state and has ruled out any pre-negotiation with the Scottish government, because it does not support independence. Creating two states from one is not just a legal matter. Domestic and international politics are also in play.

"Our first paper in this series makes the case that devolution - Scotland's constitution today - offers our country the best of both worlds. We're a strong proud nation within a modern, devolved country."

"Too often we have taken for granted what we have, so, in our paper, we set out a full and detailed examination of the devolution settlement that we have in the UK."

Mr Moore said the devolved Scottish Parliament had become an "established and trusted form of government in Scotland", adding: "Independence would end devolution - it is not an extension of it."

The Scottish secretary said he was confident more devolution for Scotland would happen, but said the UK government would not be bringing forward such proposals, arguing they should come from the "grassroots".

On the legal advice, Lord Wallace added: "The opinion from Professors Crawford and Boyle concludes that, in the event of a vote in favour of leaving the UK, in the eyes of the world and as a matter of law, Scotland would become an entirely new state.

"In international law, new or 'successor' states are regarded as fundamentally different in law from 'continuator' states.

"A successor state, in contrast with a continuing state, does not automatically inherit the rights, obligations and powers of the predecessor."

Scotland's deputy first minister, Nicola Sturgeon, told BBC Scotland "The UK government's position is staggeringly arrogant.

"The idea that if Scotland votes democratically to be independent then the rest of the UK waltzes off with all the rights and Scotland is left with nothing undermines any suggestion that we're an equal partner within the UK at the moment.

"It also begs the question, if that's true of rights, it must be true of liabilities like the UK national debt as well."

Ms Sturgeon described international law on state succession as "ambiguous", adding: "These are matters that will be settled as they have been in international precedents by negotiation and agreement."

The Scottish government is publishing a White Paper outlining the substantive case for independence towards the end of the year.

A bill setting out the terms of the autumn 2014 referendum - including the precise date - is expected to be introduced to the Scottish Parliament in March.