Girls as young as 11 are enduring working days of up to 18 hours, no or paltry pay, no statutory rights, no days off, trafficking, beatings, sexual abuse, denial of education and no private space, the group alleges in a 74-page report.

"We hear a lot about kids stitching soccer balls in Pakistan, but the conditions here are often worse," Sahr MuhammedAlly, the author of Always on Call: Abuse and Exploitation of Child Domestic Workers, told the Guardian.

"The difference is that this is hidden, because it is individuals behind closed doors in private homes who have no means of complaining."

Vina, one of the 44 domestic workers interviewed for the report, began work at 13 after her family could not afford her secondary school fees.

"I had no day off. I was always depressed because I could not leave the house to visit my mother or sister. No one came to see me. It was not allowed," she said. "My employer would give me food once a day, but if I ate more than that she would shout at me and call me pig."

Only one of the workers said she had been allowed to continue her education, even though education up to 15 is mandatory.

The International Labour Organisation estimates that at least 688,000 children are working as domestic workers in Indonesia, of whom 640,000 are girls and 275,000 are under 15.

Ms MuhammedAlly accepts that many maids are well looked after and that the government has passed some laws guaranteeing children's rights, but says there is virtually no enforcement. "If employers are not being prosecuted for abuse then there's effective impunity," she said.

Domestic maids are one of the few groups excluded from the manpower act which regulates workers' rights such as hours, pay and conditions.

The government claims it is impossible to legislate on maids because they work in the privacy of people's homes and are usually given food and lodging and treated as family. Many, the report claims, are paid less than 300,000 rupiah (£17) a month, or about 4p an hour.

The senior welfare minister, Alwi Shihab, yesterday defended child maids as a cultural phenomenon where wealthier people give poor children a head start in life. He insisted there was a system of redress. "The mechanism of complaint is running away from the problem, and they will seek their fortunes somewhere else," he said.

The ILO and Indonesian rights groups agree with Human Rights Watch. They believe the resistance to change is so strong they are compelled to focus on just fighting for a weekly day off.

"With a day off they at least can get out and communicate with others about their conditions," said Pandji Putranto, of the ILO's International Programme on the Elimination of Child Labour. "Then when people start to realise the scale of the problem we'll talk about other issues."

Muhammad Farid of the Indonesian human rights commission is pessimistic about the prospect of change in his lifetime because of "underlying factors". "[It's] the poverty, the culture, the feudalism and the law itself," he said.