Federal prosecutors accused a high-profile South Florida attorney of concocting a Ponzi scheme that lured millions of dollars from investors with promises of big payoffs from legal settlements that never existed, according to court documents filed Monday.

The civil complaint, seeking forfeiture of eight pieces of property owned by lawyer Scott Rothstein, marks the first time prosecutors have leveled fraud allegations at him_ even though criminal charges have yet to be announced. It was filed the same day FBI and Internal Revenue Service agents seized luxury cars, boats, bank accounts and other possessions of the once high-flying Rothstein. The forfeiture complaint put the value of the real estate at more than $18 million.

In the complaint, prosecutors claim that Rothstein operated the Ponzi scheme since 2005 using his law firm, Rothstein Rosenfeldt Adler. Investors were promised fat profits of 20 percent or more by paying lump sums to people who had won legal settlements that would supposedly pay out larger amounts over a longer period.

It was all a lie, the complaint contends. Like all Ponzi schemes, new investor money was used to pay earlier investors to keep up an illusion of success, backed up by false documents showing bank accounts containing fictional large sums.