Family members of Olympic athletes were among those robbed of seats at the Beijing Games after an internet scam offered thousands of fake tickets.

But the International Olympic Committee (IOC) was aware of the situation for months, but failed to act early enough, claims a US lawyer who said he had lost $12,000 (£6,000) in the fraud.

People have lost thousands paying for non-existent tickets and unnecessary airfare and Jim Moriarty, partner at a Texas law firm – who hopes to represent fellow victims in any subsequent legal actions – accused the IOC of complacency.

"They have known about these sites for months and months and did nothing," Moriarty told Reuters.

"They have dashed the hopes and dreams of thousands of people who have been planning for years to go the Games, and have already paid thousands of dollars for airfare and what they thought were legitimate tickets."

A member of the IOC board said the issue was raised last week, prompting the IOC and the US Olympic Committee to file a lawsuit accusing at least six web sites of selling fake or non-existent tickets.

But according to Reuters, www.beijingticketing.com, one of the sites accused, was still operating today, offering seats for several events including the opening ceremony on Friday.