A new report on the plight of lower caste women in rural India reveals a depressing portrait of rape, sexual abuse and harassment, and suggests that it is virtually impossible for victims even to file a complaint at a police station, let alone achieve justice.

An "extremely high" number of sexual assaults takes place on women from desperately poor Dalit or tribal communities - often by landlords, upper caste villagers and police officers, the study, published yesterday, found. But fewer than 5% of cases make it to court, activists estimate.

When the perpetrators are upper caste or come from influential local families, policemen invariably refuse to take a statement from victims - and have even been known to assault the women. They also routinely demand bribes, intimidate witnesses, cover up evidence and beat up the women's husbands.

The police also do little or nothing to prevent attacks on rape victims by gangs of upper-caste villagers seeking to prevent a case from being pursued. Sometimes the policemen even join in, the study suggests. Rape victims have also been murdered. Such crimes usually go unpunished.

The study by Amnesty International was conducted late last year in Uttar Pradesh and Rajasthan, two of the most backward and feudal states. But its findings can be applied across most of India.

Researchers found that women from so-called untouchable castes were prevented from using the same well as upper-caste villagers, or attending the same temple. Women who ignored these restrictions were often raped as punishment.

"Dalit people have been repressed for years. Even when Dalit women were raped, nobody would say anything about it," Bhanvari Devi, a Dalit from Rajasthan, said. "If a Dalit is riding a cycle or wearing shoes in front of an upper caste person, then they are harassed by members of the upper caste."

Ms Devi said that when she drew water from the upper-caste well in her village, thugs beat her 11-year-old daughter unconscious. She went to the police station to complain but was thrown out and called a "whore". A gang of upper-caste locals then sexually assaulted her at her hut that night,

The study also found that lawyers for victims of sexual assault in few cases to reach the courts would often accept money from the accused and advise their client to drop the case. Police officers routinely dismissed at least 30% of rape complaints as false.