Human Rights Watch has called on Saudi judges to overturn a decision to drop charges against a Saudi couple accused of severely abusing an Indonesian maid.
A judge in Riyadh awarded $670 damages to the maid, Nour Miyati, but dropped all charges against her employers.
The female employer, who admitted the abuse and was originally sentenced to 35 lashes, had her sentence overturned.
Human Rights Watch said the ruling on Monday was "outrageous", and sent "a dangerous message" to Saudi employers.
Ms Miyati, 25, contracted gangrene after allegedly being tied up for a month and left without food in 2005. She had to have several fingers and toes amputated.
New York-based Human Rights Watch called for an appeals court to "impose stiff penalties on the employers, including imprisonment, and payment of significant financial compensation".
Saudi officials have not commented on the report.
Human Rights Watch says Ms Miyati was treated in a Riyadh hospital in March 2005 for gangrene, malnourishment and other injuries.
All charges against Ms Miyati's male employer were dropped early in the investigation, Human Rights Watch says.
On Monday a Riyadh judge found the female employer not guilty, despite her earlier admission and "compelling physical evidence", the group says.
A prior Saudi judgement, subsequently overturned, had seen Ms Miyati convicted of falsely accusing her employers and sentenced to 79 lashes.
Human Rights Watch said the latest ruling "sends a dangerous message to Saudi employers that they can beat domestic workers with impunity and that victims have little hope of justice".
Rights organisations say many foreign domestic maids in Saudi Arabia work in harsh circumstances and often suffer abuse by their employers.
The Saudi Labour Ministry has acknowledged some problems, but the government also says foreign workers' rights are protected under Islamic law.