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."
"Our conclusion is that the White Paper does not offer a coherent vision for how or why an independent Scotland would be better off from erecting barriers between itself and its biggest export market ...
"The loss of many of the strengths of the union would open the nation to a higher risk from economic shocks. Independence would be a major economic upheaval with uncertain consequences.
"For this reason, we believe that the best way to deliver jobs and prosperity for the people of Scotland is for Scotland to remain a part of the UK. In short, Scotland and the UK are stronger together."
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.
– Alistair Darling, leader of Better Together
"This important report from the body representing our largest employers makes clear that we face an important choice in September between the strength, stability and security of being part of the bigger UK or taking a leap in the dark with independence...
"The CBI is right to call for Alex Salmond to set out a plan B on currency. A currency union isn't going to happen, as it would be bad for Scotland and for the continuing UK. We need to know what would replace the pound - would we rush to adopt the euro or set up a separate unproven Scottish currency? The idea that Scots can go to the polls blind on this most fundamental issue simply isn't credible."
However, the Scottish Government called the report "one-sided":
– Spokesman for Deputy First Minister Nicola Sturgeon
"Unfortunately, this paper misrepresents the realities of independence in several key respects - an independent Scotland will still enjoy barrier-free trade with the rest of the UK, which is in everyone's interest - and the only serious threat to our membership of the EU is Westminster's proposed in-out referendum.
"The CBI recognises the Scottish economy has key strengths - and that we are one of the wealthiest countries per head in the world - but for some reason this one-sided report ignores the positive impact of growth policies in Scotland's Future, such as giving Scottish business a competitive tax advantage, cutting air passenger duty, a sensible immigration policy, plans to transform childcare and grow the working population, increase the number of women on company boards and a range of levers necessary to counter the massively unbalanced nature of Westminster economic policy-making which favours London and the south-east of England.
"On currency, the CBI make the point that businesses want to retain a single currency, while only this week the UK Government's arguments on a Sterling area were taken apart by an independent expert who described them as 'weasel words' which are 'entirely a false argument'.
"The reality is that Business for Scotland - the pro-independence business group - has attracted more than 1,500 members since its launch just nine months ago. That is the measure of success the positive vision for the economic opportunities of independence is having in attracting business people into the Yes campaign."