The Chancellor George Osborne has been taken aback by how poorly the SNP's independence campaign has gone, according to Downing Street sources.
They said that the UK Government's chief campaign co-ordinator was "staggered" by the lack of detail coming from the Scottish Government.
A Whitehall insider likened the battle to "professionals versus amateurs".
The SNP has accused the UK Government and high-profile ministers including Mr Osborne, of "scaremongering" over independence.
The Chancellor chairs the Coalition's cabinet committee on Scotland, which co-ordinates its push against independence.
It has faced criticism after a preview of a Whitehall paper on separation warned of the possibility of mobile phone roaming charges between Scotland and England, despite the issue being tackled by the EU.
While polls suggest most Scots oppose independence, First Minister Alex Salmond has described recent debate on the issue as the "phoney war" and insisted his party's referendum campaign had yet to begin.
But Downing Street sources made clear that the Chancellor believed his campaign was "going much better than any of us could have hoped. We have created that debate".
They said it could not have been predicted "that the SNP would have so few answers," describing it as "staggering".
Mr Osborne is also understood to believe that the fight to keep Scotland in the Union is "one of the most important things that is happening in this parliament."
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