Virgin founder Sir Richard Branson said the Government must clarify the UK's trade relationship with the EU before the nation is hit with higher tariffs and taxes.
The call comes as the Virgin Group founder outlined a five-point plan for the UK economy following the Brexit vote.
In a column for The New European newspaper, Sir Richard said there was still a "feeling of uncertainty" hanging over the economy, which will continue unless the Government acts fast.
He said: "It is vitally important that UK business has some idea of how it will be able to trade with its closest trading partners and not slip back to the time before the 1970s when the UK was restricted by high tariffs and taxes."
He added: "The fortunes of UK-focused businesses have not improved and the pound remains low, forcing up the cost of imports and travel.
"The feeling of uncertainty hanging over Britain's economy has continued into the summer, as the business community waits for clearer signals from the new Government as to how they plan to rebuild long-term relations with our EU trading partners and forge new ones around the world.
"Businesses across the UK must now adapt to this new reality and look for opportunities out of the disruption caused by the vote. Over the years at Virgin, we have found periods of uncertainty and recession to be good ones to expand through."
Sir Richard's five-point plan includes action to clarify the UK's trade relationship with the EU; allowing the three million EU nationals to keep living and working across Britain; focusing on infrastructure projects outlined in David Cameron's manifesto; increasing global connectivity by pushing ahead with a new runway at Heathrow; and the expanding the Start-Up Loan scheme.
In the days after the referendum result, the billionaire businessman said Virgin Group may have lost up to a third of its value following Britain's vote to leave the EU.
He has also called on Parliament to take a second look at the referendum result.
Media publisher Archant said The New European newspaper will continue to publish on a rolling basis, following strong first week sales.
Sir Richard's column appears in this week's edition of The New European newspaper, available in print or online at www.theneweuropean.co.uk.