Former Labour first minister Henry McLeish has declared he will back Scottish independence if the United Kingdom votes to leave Europe against Scotland's wishes.

Mr McLeish said Brexit would spark a "constitutional crisis" resulting in the break-up of Britain if a Scottish majority vote to stay in the European Union is at odds with the rest of the country.

Speaking to The Sunday Times newspaper, he said the Conservatives and the SNP were both a threat to the union in different ways.

He said: "As far as the EU is concerned the Conservatives are playing with constitutional fire. If the UK votes to leave the EU and Scotland votes to stay in, then there would be a constitutional crisis.

"As a passionate European, I would not wish to be part of the UK and would anticipate a new Scottish referendum which would take Scotland out of the UK to become a new member of the EU."

He added: "If Scotland votes to stay in and we are taken out by English votes then quite frankly I'd want to be part of an independent Scotland who in turn was a new member of the European Union."

David Cameron has pledged to hold an in-out referendum on EU membership by the end of 2017, with speculation that the poll could take place as early as this summer.

Currently polling suggests the result of the ballot is on a knife edge.

A poll conducted by Survation last month showed 51% of people across the UK want to leave the EU, while 49% wish to stay.

The survey found 42% of Scots want to leave, while 58% would vote to stay.

First Minister Nicola Sturgeon has called for a requirement that all four nations of the UK have to agree to withdrawal - effectively giving Scotland a veto.

Withdrawing from the EU against Scotland's will would be likely to spark demand for a second independence referendum, Ms Sturgeon has said.

Labour's only Scottish MP Ian Murray said the referendum was a "UK membership and a UK vote".

Asked on the BBC's Sunday Politics Scotland if the EU vote could give rise to justification for a second independence referendum, he said: "I can't see where the justification would come from.

"The bottom line in terms of all of these issues with regards to referenda and independence is that the economic case for independence is worse now than it was last year.

"We have to do what is in the best interests of Scotland and the Scottish people and that is why we are campaigning to stay in Europe both at Scottish level and at UK level."

Mr Murray said that while it was clear some Labour MPs would be campaigning in the referendum to leave Europe, he was currently unaware of any MSPs who intend to do so.

Meanwhile, Conservative MSP Alex Johnstone told the programme he had not decided which side he would take.

"It depends entirely on the outcome of the negotiations the prime minister is involved in," he said.

"I think we have some serious problems in Europe at the moment. At this time, our direction in Europe is inappropriate."

He said he would be "surprised" if at this stage, any Tory MSPs would declare that they would be campaigning for a vote to leave.