Chancellor George Osborne has warned that Scotland would be worse off if it left the United Kingdom.
Mr Osborne told ITV News he did not believe an independent Scotland would be as "prosperous" as it is now.
He also questioned whether Scotland alone would have been able to bail out the RBS and HBoS banks in 2009.
He refused to say whether an independent Scotland would be allowed to retain the British currency, the pound.
Debate about Scottish independence intensified this week with arguments between politicians in Edinburgh and Westminster about the date and nature of a proposed referendum on independence.
Scottish First Minister Alex Salmond has invited the prime minister and deputy prime minister to Scotland to discuss the issue.
On Thursday, the Scottish Parliament backed calls for the terms of the forthcoming independence referendum to be decided by Holyrood.
The SNP administration in Edinburgh, which wants to leave the UK, has said it would prefer to hold a referendum on Scotland's constitutional future by the autumn of 2014,