Chancellor George Osborne has said the SNP "are tying themselves in knots" over plans to retain the pound in the event of a Yes vote next year.
In a UK Government article, co-written with Treasury Chief Secretary Danny Alexander, they said that a currency union could only work as part of a political and economic union. They also said Scotland could "of course" be independent, but that remaining in the UK is the best way to "realise aspirations".
It comes ahead of the publication on Tuesday of the UK Government's analysis of the implications for the currency of Scottish independence.
The Scottish Government has set out plans to retain the pound as Scotland's currency if the country votes for independence in next year's referendum, in what the First Minister has described as a "sterling zone" with the rest of the UK.
Economics experts in the Fiscal Commission Working Group, set up by First Minister Alex Salmond, have already concluded keeping sterling as the currency in an independent Scotland was "sensible" and an attractive choice for the rest of the UK.
In the article, Mr Osborne and Mr Alexander wrote: "This isn't a question of whether or not Scotland could go it alone - of course Scotland could. The real question is whether going it alone is the best way for people living in Scotland to realise their aspirations and provide security for themselves and their family.
"We hope very much that people living in Scotland will decide to stay. The United Kingdom has done so much together and can achieve so much more in the future. For the advocates of independence the United Kingdom doesn't work. For them all the risk and uncertainty of separation is worth it just to have control of all the decisions of a fully sovereign state. But they're tying themselves in knots.
"They know in their heart of hearts that the economic and political union we have across the UK does work. And that a formal currency union can only work with political and economic union."
Deputy First Minister Nicola Sturgeon said maintaining the pound in an independent Scotland was the "common sense position supported by the facts''.
"An independent Scotland using the pound will mean Sterling's balance of payments will be massively boosted by Scotland's huge assets, including North Sea oil and gas - which alone swelled the UK's balance of payments by £40 billion in 2011-12."