Fake shirts, flags and other souvenirs are available on South Africa's streets - often sold by traders at traffic lights.
South Africans have been encouraged to buy national team shirts to wear on special "Football Fridays" but many complain bitterly about the high cost of official Adidas jerseys. Copies sold by hawkers are popular.
"Despite efforts to clamp down on counterfeit goods coming mainly from China and other Asian countries, fake jerseys and other merchandise for national teams will be costing bonafide suppliers millions of dollars in lost revenue," the International Authentication Association (IAA) said in a statement.
"The problem of fake goods at this ... World Cup is a big concern," he said.
"We are urging all those involved in the fight against counterfeiting, from anti piracy and law enforcement agencies to official suppliers to review their security plans."
