The bosses of more than 100 Scottish companies have thrown their weight being the campaign for the union.
They have concluded the risks of separation are far too high, citing uncertainty over issues like currency and EU membership.
Those giving their support to the Better Together campaign include John Boyle, chairman of investment company The Hamilton Portfolio, fashion designer Belinda Dickson and Daniel Johnson, owner of the Paper Tiger and Studio One retail chain.
Mr Boyle said as part of the “most successful union in history for over 300 years”, Scotland had “punched way above its weight”.
“The Scots have delightful competition with, but friendly and infectious allegiance to, our English partners and the idea that all of this should be thrown away at such a pivotal time in the United Kingdom’s history is quite simply preposterous,” he said.
“There are demonstrably no economic benefits and the demise of the union could see us struggle as we lose all the benefit of this unique relationship blended over hundreds of years.”
Ms Dickson, founder of BJD Design, said: “I can see no benefit in Scotland isolating itself from the rest of the UK.
“There are far too many unanswered questions if independence were to go ahead on the pound, Europe, defence, trade agreements, simplicity of movement of both goods and people. Quite frankly why would we take the risk?”