Gordon Brown is stepping up his role in the independence campaign, after burying the hatchet with his former Downing Street neighbour Alistair Darling.
The former Prime Minister has asked the leader of the Better Together campaign, Mr Darling, to commission analysis to stress-test the Scottish Government's key proposal of a currency union between an independent Scotland and England.
The tests would be along the lines of Mr Brown's "five economic tests" for Britain joining the eurozone posed when Labour came to power in 1997.
The tests, which were never met, asked: could there be sustainable convergence between Britain and the eurozone; was there sufficient flexibility to cope with economic change; what would be the effect be on UK investment; what would be the impact on the financial services sector; and was it good for jobs, stability and growth?
Danny Alexander, the Chief Secretary to the Treasury, said there was "no clear economic rationale" for a currency union between the UK and an independent Scotland.
The LibDem minister said that the so-called "fiscal gap" in an independent Scotland, identified by the Institute for Fiscal Studies and put at 1.9% of national income compared to 0.8% for the UK, would mean a break-away Scotland would need to grow at almost 2% a year more than the UK for the next 50 years in order to eradicate the gap.
"Over the past 50 years Scotland and the rest of the UK have grown, on average, at an almost identical 2% per year. So it would be necessary to double this rate," explained Mr Alexander.
"This would be at the same time an independent Scotland's economy would be facing greater pressure from the decline in North Sea production and an ageing population.
"No European country has managed to grow at the required rate of 4% over the past 50 years."
Labour sources have made clear the ex-PM will be a major presence in the pro-UK campaign with one making clear he will up his contributions significantly as we near September 18.
Another said Mr Brown, much more highly regarded north of the Border than south, would bring "poetry" and "emotion" to the debate.
l Mr Brown has claimed £1012 over two months last year for the rent of his Kirkcaldy and Cowdenbeath constituency office, the latest audit of MPs expenses has revealed.
Why are you making commenting on The Herald only available to subscribers?
It should have been a safe space for informed debate, somewhere for readers to discuss issues around the biggest stories of the day, but all too often the below the line comments on most websites have become bogged down by off-topic discussions and abuse.
heraldscotland.com is tackling this problem by allowing only subscribers to comment.
We are doing this to improve the experience for our loyal readers and we believe it will reduce the ability of trolls and troublemakers, who occasionally find their way onto our site, to abuse our journalists and readers. We also hope it will help the comments section fulfil its promise as a part of Scotland's conversation with itself.
We are lucky at The Herald. We are read by an informed, educated readership who can add their knowledge and insights to our stories.
That is invaluable.
We are making the subscriber-only change to support our valued readers, who tell us they don't want the site cluttered up with irrelevant comments, untruths and abuse.
In the past, the journalist’s job was to collect and distribute information to the audience. Technology means that readers can shape a discussion. We look forward to hearing from you on heraldscotland.com
Comments & Moderation
Readers’ comments: You are personally liable for the content of any comments you upload to this website, so please act responsibly. We do not pre-moderate or monitor readers’ comments appearing on our websites, but we do post-moderate in response to complaints we receive or otherwise when a potential problem comes to our attention. You can make a complaint by using the ‘report this post’ link . We may then apply our discretion under the user terms to amend or delete comments.
Post moderation is undertaken full-time 9am-6pm on weekdays, and on a part-time basis outwith those hours.
Read the rules hereComments are closed on this article