"I am the victim of a lynching organised by the judicial counselor of the government (Menahem) Mazouz, the police, politicians and the media," Katsav said in the televised press conference.
"My honour, and that of my family, has been attacked for the past three years. I have been humiliated, crushed, knocked down, and I suffer. But I am determined to fight to ensure that the truth emerges, all the truth, because I am innocent."
Mazouz, who is also attorney general, announced on Sunday that Katsav will be indicted on charges including rape in the latest act of a years-long saga.
Katsav said the "institutions of the state have joined together against me on the basis of false testimony, contradictory facts, lies, fabricated evidence and, above all, baseless rumours."
Mazouz's announcement marked the latest chapter in an affair that began in 2006, when Katsav claimed a former employee was trying to blackmail him.
An investigation resulted in the woman accusing the president of raping her while she was his secretary in the late 1990s.
The accusations and the months of investigations that followed saw Katsav embroiled in the worst scandal ever to befall an Israeli leader as other women levelled similar charges.
Amid the uproar, Katsav removed himself from duties in January 2007, following a very public row with the state prosecution.
In February 2008, the Supreme Court accepted a highly controversial plea deal and Katsav was charged with sexually harassing two women and performing indecent acts.
But when he went on trial on April 8, 2008, he announced that he was withdrawing from the agreement.
If convicted of rape charges, Katsav can face up to 16 years in jail and would become Israel's first head of state convicted of sex offences.
He is already the second president to be forced out by scandal.
The late Ezer Weizman was forced to resign in 2000 after revelations he received around 450,000 dollars from a French millionaire while a minister and an MP.
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