The head of the Confederation for British Industry (CBI) said his organisation supported Scotland staying part of the UK because the Scottish Government's proposals for independence "do not add up" .
John Cridland, director-general of the CBI, said the White Paper published last November "lacked clarity", which could put an independent Scotland's future success in jeopardy.
He said the Scottish government's immediate policy plans were fiscally neutral, but in the long-term the yes campaign had set out £670m of "unfunded" spending commitments.
The business organisation also argued a Yes vote in September's referendum would "open key sectors of the Scottish economy to increased risk".
It dismissed Scottish Government plans to keep the pound in a currency union with the rest of the UK as "not viable", with this having been rejected by Chancellor George Osborne and his Labour and Liberal Democrat counterparts.
Despite that, the CBI said "we have not seen a plan B" on currency from Holyrood ministers.
It claimed that "breaking up" the UK internal market would increase costs for businesses and consumers on both sides of the border, and said an independent Scotland was unlikely to enjoy a "smooth process" to membership of the European Union, and its "terms of membership could leave it worse off".
Mr Cridland said: "The minute you draw a line between Gretna and Berwick, Scotland starts to drift apart from its biggest market and loses a significant amount of economic clout.
"The economic plan outlined in the White Paper does not add up. It ignores the need for deficit reduction, instead promising more unfunded spending.
"On the key issues that are critical to jobs and growth, the White Paper's lack of clarity runs the risk of jeopardising an independent Scotland's future success."
He added: "Keeping the pound is the best option for Scotland but that is only on offer through maintaining the union. The main UK political parties have ruled out currency union as an option, so we're calling on the Scottish Government to set out a credible plan B."
Mr Cridland also said: "An independent Scotland would also have to negotiate hard to get back into the EU, temporarily losing access to the world's biggest trade area with huge economic consequences."
About the Confederation of British Industry:
- Lobbying organisation calls itself "the voice of business"
- Represents 240,000 firms across the UK
- Its members employ 50,000 people in Scotland
The leader of the Better Together campaign and former Chancellor of the Exchequer Alistair Darling welcomed the report.
However, the Scottish Government called the report "one-sided":