A Scotland-based company which employs 3,500 people around the world has threatened to move its headquarters elsewhere if independence is voted for.
Alan Savage, chairman of the the Orion Group, said he would personally live in an independent Scotland but the "uncertainty" over currency, trade, tax and EU membership may involve "running the business from somewhere else".
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The Inverness-based recruitment boss is a former chairman of Inverness Caledonian Thistle football club, and donor to the pro-UK Better Together campaign.
In an article for the Huffington Post, circulated by Better Together, Mr Savage said: "Uncertainty is a nightmare for anyone running a business today.
"My company, run out of Scotland with 1,500 workers across the UK and 3,500 globally, needs economic and political stability to keep it healthy and allow us to continue to invest in a world-class workforce.
"We need certainty on a wide range of business-crucial areas, including embassies, trade, tax, and membership of the EU. Being part of the UK has given Scottish-headquartered companies like Orion certainty on these issues.
"The Scottish Government's White Paper wish list for independence doesn't give business any assurances on these 'must dos'.
"But for me the biggest uncertainty of all in Mr Salmond's separation experiment is on the vitally important issue of currency.
"However, Alex Salmond's point blank refusal to set out a currency plan B, as well as his reckless threat to default on our debt if he doesn't get his eurozone-style currency union, means that I have to come up with a plan B of my own.
"This would involve still living in Scotland, but running the business from somewhere else."
The SNP said the Huffington Post article is a rehash of claims Mr Savage made several months ago.
A spokesman said: "An independent Scotland will keep the pound, and will offer huge opportunities for business - as underlined by the more than 1,300 business people who have joined the pro-independence Business for Scotland group.
"And the only uncertainty facing Scottish businesses is Westminster's threat to drag Scotland out of the EU against our will, with all the disastrous consequences for jobs, investment and prosperity that would entail."