About 30,000 migrant workers hired by farms in Israel pay thousands of dollars to middlemen for their jobs but earn less than the minimum wage and are cheated out of overtime, according to an Israeli rights group report.

The rights group Kav LaOved says the workers come mostly from Thailand but also Nepal, Sri Lanka and the Palestinian Territories.

Its report calls them "the most exploited segment of workers in Israel". The findings were due to be presented to the Israeli Knesset this week before parliament rules on a request for more employment permits from farmers and agri-businesses.

"The farmers are fighting for more employment permits but most of them violate the workers' most basic rights," the report says. The vast majority of migrants work more hours than the law allows without being paid for overtime.

The group said its findings are based on "hundreds of complaints by agriculture workers and dozens of inspections by Kav LaOved volunteers at work sites around the country".

"The Thai workers come from rural areas after paying middlemen in Thailand and Israel brokerage fees running from $8,000-10,000," the report says.

"Most of them come to Israel and immediately begin working in remote and isolated locations, without knowing basic aspects of Israeli law."

According to Kav LaOved, "the most common complaint among agricultural workers is that their wages, especially the Thais', are withheld for months, or sent to their home countries without them receiving any accounting".

Some employers allow only one day off per month and no paid vacation, and the withholding of passports while "strongly condemned" by legal authorities, is still commonplace, the report adds.