The former presidential hopeful has admitted attending sex parties there, but says he did not know that some of the women were paid prostitutes.
The case is the last of the sex-related allegations faced by Mr Strauss-Kahn.
A series of lurid claims have been made about the high profile French figure since he was arrested in New York in May 2011 after a hotel maid said he had tried to rape her.
Charges were eventually dropped, and Mr Strauss-Kahn subsequently reached a settlement with the maid, Nafissatou Diallo.
Two other cases against him have also been dismissed.
An allegation of sexual assault in Paris in 2003 was not pursued because it had taken place too long ago.
And in October last year, French prosecutors ended an investigation into allegations of gang rape at a hotel in Washington after the woman who made the claim retracted her evidence.
French prosecutors recommended last month that the Lille allegations – known as the Carlton affair after the hotel where the orgies allegedly took place – should be dropped.
The latest announcement makes clear, however, that the legal difficulties of the disgraced politician are not yet over.
The investigating magistrates are not obliged, in the French legal system, to follow the advice of the prosecutors, and on this occasion they have not.
Mr Strauss-Kahn was originally under investigation for “aggravated pimping as part of an organised gang”. He is now facing the slightly less serious charge of “aggravated pimping as part of a group,” along with 12 others.
His lawyer told Le Monde that the legal team was “under no illusions” as to the relentlessness shown by the magistrates towards their client.
“This decision is based on an ideological and moral analysis, but certainly not on legal grounds,” he said.
“We will demonstrate in the criminal court that it is a total aberration.”
Mr Strauss-Kahn, who stepped down as International Monetary Fund leader after his arrest in New York, had looked like a plausible Socialist challenger for last year’s presidential elections.