Iain Duncan Smith says an independent Scotland will have to raise taxes or increase borrowing to plug a pensions black hole.
In a speech today, the Conservative Welfare and Pensions Secretary will claim a stand-alone state faces problems with an ageing population and a smaller tax base.
The Treasury has calculated that by 2060 Scotland will have just 1.9 working people for every pensioner, compared with 2.2 in the rest of the UK.
Mr Duncan Smith will say: "The SNP has some serious questions to answer. How would they pay for this? More borrowing? Higher taxes?
"United, the UK is in a stronger position to respond to these challenges, sharing the resources and risks. It gives people certainty there is a secure welfare safety net in place - one which will endure in the future."
He will also highlight a leaked memo in which Scottish ministers privately voiced concerns over the welfare issue.
The UK Government says each working-age person pays taxes worth around £2800 a year to help the state fund pensions and other pensioner benefits, such as the winter fuel allowance. Over the next 50 years, that is estimated to rise by £700 a year. In Scotland, that figure would be £1100 more.
Meanwhile, Citizens Advice Scotland has warned the UK Government's welfare reforms will have a "devastating" impact on benefits claimants. Disabled people and their families stand to lose a total of more than £1 billion in benefit payments, the charity said.
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