Scottish independence would lead to "years of upheaval" for firms on both sides of the border, according to a business lobbying group.
The Confederation of British Industry (CBI) says it is "not convinced of the business and economic case" for independence.
During a speech in Glasgow on Thursday evening, CBI director-general John Cridland will voice his concerns about Scotland leaving the UK.
He will stress Team GB's success at the Olympics, saying that was an example of how Scotland and England can achieve more together.
Addressing the CBI Scotland annual dinner, Mr Cridland will say: "The CBI has a collective view on independence and, I believe, a duty to express it. CBI Scotland council is not convinced of the business and economic case for Scotland seceding from the Union and judges that businesses - Scottish, English, British - would lose out from the fragmentation of our single market.
"We have two years to get this right, and get it right we must."
If people in Scotland vote to leave the UK, the CBI would "work with the mandate". But a Yes vote would bring "several more years of upheaval and negotiation", he will argue.
"The immediate effects would be profound and, in the short term, costly. When Slovakia separated from the Czech Republic, it cost the country 4% of its GDP in the following year."
Uncertainty is the "biggest bogeyman of all" for business and the debate over Scotland's future is "adding a thick layer of uncertainty", he will say.
"What's on offer here is often described as divorce. Those proposing a permanent split say there's no animosity in this. It's just that after 300 years of relatively happy marriage, they feel it's time we started seeing other people. My view is: that's the wrong way to look at it.
"Yes, there are differences, as there are in any marriage. But if the differences were all we focused on, few relationships would last long."
What is "more important, and much more positive, are those things we like doing together. If we like winning at sport, and we do, then competing as one team has shown itself to be a great source of patriotic pride.
"Edinburgh-born Chris Hoy or Glasgow-born Andy Murray of course add an extra golden glow here north of the border. But they won gold for all of us, just as Mo Farah, Jessica Ennis and Ellie Simmonds did.
"If 2012 was the grand finale for Team GB, I'm not sure anyone outside political circles has been asked what they think about this."
A spokesman for Finance Secretary John Swinney said: "The only uncertainty being caused to Scottish businesses at the moment is through the dismal economic policies of the UK Government and their failure to properly invest in capital projects.
"The reality is that Scotland is the most attractive place anywhere in the UK for inward investment for the second year in a row.
"Many business leaders have made clear they see great opportunities with independence. Scotland urgently needs responsibility for the key economic levers required to boost economic recovery and create jobs, and many of the leading job creators in Scotland agree with us on that."
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