Almost half of British businesses in a new poll believe the costs of complying with European Union rules outweigh the benefits of EU membership.
The survey was commissioned by the Business for Britain campaign, which supports Prime Minister David Cameron's promise to renegotiate the terms of UK membership and put it to a referendum.
A sample of 1,024 firms asked by YouGov took the stance by a margin of 46% to 37%, with a clear majority (56%) saying meaningful reform required treaty changes and a return to a trade-based deal.
The pledge of an in/out public vote by 2017 should the Conservatives win the next general election was backed by 66% to 26%.
Chief executive Matthew Elliott said: "It will come as a surprise to many that a nationwide and representative poll of business leaders finds a clear majority support EU treaty change and a return to a trading relationship.
"The reason is clear: most business leaders think the costs of the Single Market outweigh its benefits.
"Now that business has spoken, the pressure is on the Government to get a better deal from Brussels and make life easier for Britain's job creators."
YouGov polled 1,024 business leaders, broadly representative of the sizes, sectors and locations that comprise the UK business community