The Association for Democratic Reforms (ADR) study was released on Thursday as political parties lined up to condemn the rape of the 23-year-old woman, which has triggered widespread protests against how women are treated in India.
Prime Minister Manmohan Singh, the ruling Congress party chief Sonia Gandhi and opposition lawmakers have condemned the savage assault last Sunday but the ADR said many Indian parties fielded candidates who were facing rape accusations.
"Since 2007, political parties gave tickets to 20 rape accused to fight in state elections. This is shocking and requires urgent action," Jagdeep Chhokar, the founder of ADR, said.
"The politicians who come out to condemn rape are the ones who are openly giving the rape accused a chance to fight elections. This is hypocrisy," he told AFP.
The report stated that political parties had also given tickets to 260 men who were charged with other crimes against women, including molestation.
It did not record how many of the accused candidates had been found guilty.
"Political parties should stop giving tickets to candidates with criminal backgrounds and all those lawmakers who are accused in rape cases should be thrown out of power," Chhokar added.
Further protests were held in New Delhi on Friday, with scores of female demonstrators marching to the president's palace.
The rape victim was coerced onto the off-duty bus and raped by six men before being thrown off the vehicle.
She was seriously injured and remains in intensive care.
Five people, including the bus driver, have so far been arrested.