HSBC's Chairman warned that Scottish independence will leave the country's financial system in a "parlous state" as severing the 307-year old union will lead to a capital flight.
Douglas Flint added that investors and firms are likely to relocate capital as the uncertainty over how Scotland would cope without the pound and a currency union would be too much of a risk.
Scottish people will vote in an independence referendum on 18 September, 2014, and will be asked the straight "yes/no" question: "Should Scotland be an independent country?"
The Scottish National Party (SNP) has consistently promised voters that the country would still retain the pound in the event of independence.
However, all main political parties have supported Chancellor George Osborne's statement; "walk away from the UK, and you walk away from the pound."
Writing a column for the Telegraph newspaper, Flint said that the political parties' decision to bar an independent Scotland from keeping the pound was "wholly consistent with the actions that have been taken in the aftermath of the financial crisis" and "with the knowledge gained from recent events in the eurozone."
Recently, the Adam Smith Institute (ASI), which promotes free market ideas, said in a report that Scotland's economy would be better off and its financial sector more secure if it used sterling unilaterally.