It means 47% of small companies – employing fewer than 250 people – want the UK to remain in Europe.
The poll by the Federation of Small Businesses came as a report by consultants Capital Economics found ditching the EU would not be a disaster.
Fears of the economy falling into chaos by a “Brexit” were “overdone”, it said. And it slammed “scaremongering” about the impact.
Prime Minister David Cameron has said a vote will be held by the end of 2017.
Vicky Redwood, of Capital Economics, said: “We doubt an EU exit would spell disaster for UK exports, even if the UK failed to negotiate a free trade agreement. The cost of EU tariffs imposed would be manageable.”
She said the most inaccurate figure banded about was that a Brexit would lead to three to four million job losses, as it was based on all exports to the EU ending.
READ MORE: Shock poll reveals Britain would quit the European Union if referendum was held tomorrow
The report suggested the £10billion saved from not paying into the EU budget could be used to help firms affected by a drop in trade.
The FSB insists it is neutral on the debate, unlike fellow business group the CBI, which was criticised by Business Secretary Sajid Javid for having a pro-European stance.
Tim Tozer, chairman and managing director of Vauxhall, which employs 35,000 people in the UK, said the outcome would not affect the car giant.
He said: “It would be unthinkable that no trade agreement would be negotiated if this country chose to leave.”
Robert Oxley, of Business for Britain, said: “A majority of businesses are unhappy with the EU status quo and want to see the UK take control back.”
