Pension and insurance giant Standard Life has warned it may quit Scotland if voters back independence.
The finance firm is setting up contingency arrangements to protect its operation unless concerns over currency and regulation are sorted out to its satisfaction.
One of its main worries is the impact of failing to secure a joint-sterling zone, which has been rejected by Chancellor George Osborne along with the Liberal Democrats and Labour.
The revelation sparked warnings that thousands of Scottish jobs were being threatened by separation as other companies may follow suit.
But First Minister Alex Salmond insisted Standard Life’s concerns showed why the SNP’s desire for a currency union was the best option for the UK as a whole.
And he refused to budge on his belief the UK Government is “bluffing” and will agree to share the pound if voters back separation on September 18.
Standard Life – which has been based in Scotland for 189 years – is the first major company to warn independence may force it to move its centre of operations.
It has started work to establish additional registered companies to operate outside of Scotland, into which to transfer parts of its operation.
Chief executive David Nish said: “This is a precautionary measure to ensure continuity of our businesses’ competitive position and to protect the interests of our stakeholders.”
The disclosure is regarded as significant in the independence debate. The company has £240billion in assets and is the UK’s biggest provider of defined contribution pensions and self-invested pension plans.
Mr Nish stressed the company was “politically neutral” but insisted it had a duty to assess the impact of independence on its 4million UK customers, 1.5million shareholders and 5,000 Scottish-based staff.
In a further blow to the SNP, RBS warned independence would probably hit its credit ratings, impacting on costs.
The news sparked clashes in the Scottish Parliament with Labour and the Conservatives warning jobs were threatened by the SNP’s independence campaign if major employers emulated Standard Life.
Mr Salmond said the Scottish Government had put forward the concept of a shared currency and a regulatory framework “which are exactly the sort of things that Standard Life has been calling for”.
He argued Standard Life would find an independent Scotland a “good place to do business” and other major financial figures agreed.
Scottish Labour leader Johann Lamont said: “Standard Life is actively making plans to leave Scotland if the First Minister gets his way. No amount of bluff, bluster and bullying from Alex Salmond can change that fact.”
Scottish Tory leader Ruth Davidson ran through list of companies which had sounded warning, including Asda, RBS and BP.
“The SNP shouldn’t dismiss those voices or shout them down,” she said.
“Standard Life has said jobs could go in an independent Scotland if they aren’t given clarity on five major issues, so what can the first minister tell them today that he couldn’t tell them yesterday?”