A Hong Kong mother of two who punched her maids, beat them with mops and threatened to kill their relatives has been jailed for six years in a case that triggered outrage and exposed the plight of millions of domestic helpers across Asia.

Former beautician Law Wan-tung, 44, looked stunned as the sentence was passed after being found guilty of 18 of 20 abuse charges. She was also ordered to pay a £1,200 fine.

The charges included inflicting grievous bodily harm and criminal intimidation against Erwiana Sulistyaningsih and an another maid, also from Indonesia.

Law looked emotionless as she was led out of court. She had pleaded not guilty to the 20 charges but had admitted one of not buying insurance cover for her maid.

Judge Amanda Woodcock read out her verdict saying "damning evidence" revealed "how little care and kindness the defendant showed" for Ms Erwiana.

The brutality meted out to Ms Erwiana has sparked calls for Hong Kong to revise its policies on migrant workers. Around 30 supporters of Ms Erwiana protested outside the court.

Ms Erwiana had told media she would forgive her former boss but she said six years was not enough.

"It seems that while we recognise maltreatment of migrant workers as bad and that slavery exists in Hong Kong, the Hong Kong government seems to tolerate it," she said outside the court.

"With this sentencing, it is as if the people in government are okay with it."

Ms Erwiana, who arrived in Hong Kong in 2013, returned to Indonesia in January last year where doctors said burns on her body were caused by boiling water.

Photographs of a battered Ms Erwiana posted online sparked outrage and Indonesia's then president, Susilo Bambang Yudhoyono, described her treatment as torture.