Dominique Strauss-Kahn has maintained that his sexual encounter with a New York hotel maid did not involve violence, constraint or aggression but still constituted a moral failing on his part.
The former International Monetary Fund Managing Director gave his first interview since his 14 May arrest over accusations of sexual assault.
Mr Strauss-Kahn told France's TF1 television channel "what happened was more than an inappropriate relation. It was an error. I regret it infinitely and I don't think I am finished with regretting it".
He told TF1 interviewer Claire Chazal, a friend of his wife Anne Sinclair, that he was a changed man.
"I have paid heavily for it. I am still paying for it. I have seen the pain I have caused around me and I have reflected deeply," he said.
However, he maintained the encounter with the maid, Nafissatou Diallo, was consensual and that she "lied" in accusing him of attacking her after she came into his room at New York's Sofitel hotel to clean.
Mr Strauss-Kahn also dismissed as "imaginary" separate claims by a French writer that he tried to rape her during a 2003 interview, again insisting "no act of aggression, no violence" had taken place between the two.
The writer, Tristane Banon, has maintained she and Mr Strauss-Kahn tussled on the floor during an interview in an empty apartment, with the politician trying to open her jeans and bra and putting his fingers in her mouth and underwear.
Because a police investigation into the claims is ongoing, Mr Strauss-Kahn said he would not say anything more about the matter.
If Paris prosecutors decide to pursue the case, Mr Strauss-Kahn - once among the big names of France's Socialist party who was widely considered a top contender in next year's presidential race - could face a possible trial.
New York prosecutors dropped all criminal charges against him in the Diallo case last month, although Mr Strauss-Kahn is still facing a lawsuit brought by the maid, an immigrant from Guinea.
Asked whether he had any intention of returning to politics, Mr Strauss-Kahn said he would "take time to reflect" and rest first.
"But all my life was consecrated to being useful to the public good," he said, adding "we will see."
