FRESNO, Calif. - Female farmworkers across the United States are commonly sexually harassed and assaulted, in part because their immigration status makes them fearful of calling police, according to a report being released Wednesday by Human Rights Watch.

"Our research confirms what farmworker advocates across the country believe: sexual violence and sexual harassment experienced by farmworkers is common enough that some farmworker women see these abuses as an unavoidable condition of agricultural work," said the report by the international rights group.

The report describes incidences of rape, stalking, fondling and vulgar language used against women, who say they often don't report it because they are afraid of being fired or deported.

An estimated 630,000 of the 3 million people who perform migrant and seasonal farm work are female. The federal government estimates that 60 per cent of them are illegal immigrants.

"It's easiest for abusers to get away with sexual harassment where there's an imbalance of power, and the imbalance of power is particularly stark on farms," the report's author, Grace Meng, told The Associated Press.

The report calls on Congress to pass laws protecting immigrant farmworker women, and for the U.S. Department of Homeland Security to repeal rules that encourage local police to report federal immigration violations.

Meng interviewed 52 farmworkers and 110 attorneys, social service providers, law enforcement officials and members of the agriculture industry in New York, North Carolina, Florida, Texas, Colorado, Ohio, Arizona, Pennsylvania, Tennessee, and the state of Washington, but she focused primarily on California because of its large farmworker population.

Women who work for labour contractors are more vulnerable than those who work directly for a farmer, the report said.

"The goal of our report was to show that this was a national problem. And to show the governmental barriers that exist to reporting these crimes and abuses. And to demonstrate it's a human rights problem," Meng said.

Incidences are rarely reported to authorities, said Amparo Yebra of the non-profit Westside Family Preservation Services Network in California.

"We have had a lot of complaints," said Yebra. "Most of the people are farmworkers, but if they get the opportunity to get out of the fields to work in a store, some of the owners take advantage of those people also."