The UKIP leader said: "There is this deeply flawed view that leaving the EU would somehow mean a sudden end to trading with Europe.
"The CBI does not consider the more realistic option that if we left the single market and freed ourselves from its red tape and politicised agenda we would still be able to continue to trade strongly with Europe on our own terms.
"Instead the CBI are proponents of this skewed view that Britain can renegotiate terms with the EU to create a more streamlined relationship.
"That would have to involve treaty change but the European Commission President Jose Manuel Barroso has ruled that out.
"Without treaty change there can be no significant renegotiation at all."
"We have looked beyond the political rhetoric to examine the pros and cons of EU membership and British business is unequivocal - the Single Market is fundamental to our future.
"We are better off in a reformed EU than outside with no influence. Each year, membership is worth £3,000 to every household in this country.
"But the EU isn't perfect and there is a growing unease about the creeping extension of EU authority. Europe has to become more open, competitive and outward-looking if we are to grow and create opportunities and jobs for all our citizens.
"Contrary to popular myth, the UK is influential in the corridors of Brussels and will still be as long as we play our cards right. The Single Market is a great British success story and the best way for us to remain a leader on the world stage is from within the EU."
Staying in the European Union is "overwhelmingly" in Britain's interest, although reforms are urgently needed, business leaders have said.
The Confederation of British Industry has highlighted research showing that EU membership was worth between £62 billion and £78 billion, around 4-5% of the UK's total economic output.
But the business group, which holds its national conference in London today, called for a number of reforms, including removing barriers to e-commerce, becoming more outward-looking and re-focusing the work of EU commissioners.
The CBI also proposed a moratorium on legislation which could be made at national level, and a permanent UK opt-out from the Working Time Directive.