Millions of pounds will be lost without stronger links with the European Union (EU), the Guernsey International Business Association has said.
The States has been asked by the island's Policy Council to put £200,000 into raising the island's political profile in the EU.
Paul Meader, chairman of the business association, said issues being debated by the EU could affect the island.
He said firming up relations was the only way to protect local interests.
Mr Meader said: "I think the threat is very real and my concern is that £200,000 is not remotely enough money to do this job properly."
The move to increase Guernsey's political presence on the international stage could include an office in Brussels and more collaboration with Jersey.
The States is due to discuss the proposal, which is part of the States Strategic Plan, at its October meeting.