The sexual encounter four months ago in a New York hotel room with a maid was a "moral failing on my part" but was not sexual abuse, he said in a live prime-time television interview.
He said he had not finished regretting what had occurred between him and the chamber maid in his hotel but took the opportunity to repeatedly call her a liar, Al Jazeera reports.
"There were no injuries, no sign of violence, not a scratch" he said on TF1.
The former International Monetary Fund head spent two weeks with advisers and lawyers planning the interview, billed as "the moment of truth" by a former lieutenant, and Socialist deputy, Jean Marie Le Guen, BBC reports.
The interview follows the first televised debate on Thursday of the main Socialist candidates, who are now running for the presidency in his place.
There have been bids from every major broadcaster in the world but decided upon a person his loyal wife, Anne Sinclair, was friends with, Claire Chazal, at TF1.
He arrived for the interview through the back entrance of the building, avoiding the small group of protesters who chanted "DSK shame on you" and "TF1 accomplice".
And if the interview was carefully scripted or choreographed - his critics believe it was - there was never any doubt what the main question would be. What really happened in that hotel room?
He must have pondered the answer for weeks. The sexual encounter was a "moral failing on my part" he explained. But "it was not sexual abuse. There were no injuries, no sign of violence, not a scratch".
"You can read it here," he said, waving the prosecutors report.
He was critical of the U.S. justice system, in particular the "perp walk".
Before the interview, a poll published by Le Journal du Dimanche suggested that 53% of French people had wanted him to retire from politics.
Before May, Dominique Strauss was a very strong candidate for the presidency.
He said his May 14 sexual encounter with Nafissatou Diallo, an African immigrant who claimed that he attacked her when she entered his room in Manhattan's Sofitel hotel to clean it, "did not involve violence, constraint or aggression", the Press Association reports.
However, he acknowledged, it "was a moral failing and I am not proud of it. I regret it infinitely. I have regretted it every day for the past four months and I think I'm not done regretting it" AP reports.