Throughout his 18-month trial, Katsav was portrayed as a sexual predator who routinely harassed female staff [AFP]

Israel's Supreme Court has upheld the conviction by a Tel Aviv court of former president Moshe Katsav over two counts of rape and other sexual offences.

Reading out their decision on Thursday, the three justices unanimously ruled that the disgraced president was guilty of rape and rejected his "alternative scenarios," Israel's army radio reported.

In August, Katsav appealed a December 2010 conviction on charges of rape, sexual harassment, indecent acts and obstruction of justice.

He also challenged a seven-year prison sentence, handed down in March, as well as a two-year suspended sentence and an order he pay compensation of $28,000 to the main victim, known only as "Aleph", as well as $7,000 to a second victim.

Throughout the 18-month trial, Katsav was portrayed as a sexual predator who routinely harassed his female staff.

He denied the charges against him, saying he was the target of a media plot and that his interactions with his female staff were consensual.

Katsav was scheduled to begin serving his prison sentence on May 8, but Supreme Court justice Yoram Danziger had agreed to delay it until after his appeal.

He was allowed to remain free until after the appeal ruling, but will begin serving his sentence on December 7, Israeli media reports said.