French journalist and writer Tristane Banon, who once branded Strauss-Kahn a "rutting chimpanzee", indicated she would send "a complaint for attempted rape" against him to prosecutors, likely on Tuesday, her lawyer David Koubbi told the news magazine L'Express on its website.
But Strauss-Kahn, who resigned from his post at the IMF after being charged with sexual assault in New York, fired back that he had taken note of Banon's claims but dismissed them as "imaginary", his lawyers Henri Leclerc and Frederique Baulieu told AFP in a statement.
They said they "were in the process of compiling a libel complaint against her."
The prospect of a new criminal complaint against Strauss-Kahn came as the case in New York, where he was recently released from house arrest on charges of trying to rape a hotel maid, looked set to collapse after prosecutors revealed they had doubts about the credibility of his accuser.
Noting the developments in New York, Strauss-Kahn's lawyers said Banon's complaint "comes at a time when the untruthful nature of the accusations he faces in the United States are no longer in any doubt."
Koubbi told AFPTV that Banon "took that decision because she endured what she accuses Dominique Strauss-Kahn of and in France as elsewhere when you are a victim of an attempted rape, you must file a complaint."
Banon herself told the L'Express website that "today, seeing Strauss-Kahn freed (from house arrest) then afterward dining in a fancy restaurant with friends, that makes me sick."
In February 2007, Banon was a guest on a television chat show and recounted how a senior politician a few years before had lured her to a virtually empty apartment in the guise of agreeing to give an interview and then assaulted her.
In the broadcast version of Banon's comments the name of the politician was bleeped out, but a year later Banon confirmed to the AgoraVox website that she was referring to Strauss-Kahn.
"I put down the recorder straight away to record him. He wanted to hold my hand while he replied, because he told me 'I wouldn't be able to manage unless you hold my hand'," she alleged in the Paris Premiere broadcast.
"Then the hand went to my arm, then a bit further, so I stopped straight away," she explained. "It finished very violently -- as I told him clearly 'No, No!' -- and we finished up fighting on the floor.
"There wasn't just a couple of blows. I kicked him, and he tried to unclip my bra, to open my jeans," Banon alleged, adding that she eventually escaped and considered pressing charges before abandoning the idea.
Banon's mother, Socialist politician and blogger Anne Mansouret, confirmed to the news website Rue89, that she had advised her daughter at the time not to make a formal complaint for fear of hurting her career in journalism.
Koubbi referred to the attack as taking place in 2003, although her mother has previously said the incident occurred in 2002.
Banon also says then Socialist Party chief Francois Hollande was aware of the accusations, as her mother has said, but on May 20th Hollande denied "ever knowing such grave facts" as Banon has claimed.
Before his arrest in New York, Strauss-Kahn, a Socialist heavyweight, polled as the person most likely to beat President Nicolas Sarkozy in the 2012 election.
But Koubbi denied the decision to move forward with a complaint now was driven by political motives or influenced by the unravelling of the New York case.
"Even if (the New York) case against Mr Strauss-Kahn turns out to be unfounded, ours is not. It is extremely solid and backed up," L'Express quoted him as saying.
Kenneth Thompson, who is representing the hotel maid accuser in New York, applauded Banon's decision to file a sexual assault complaint against Strauss-Kahn.