Families have the right to use hidden cameras to spy on their domestic helpers if they suspect them of causing mischief or harm, the Privacy Commissioner said yesterday. But commissioner Stephen Lau Ka-men said there must be evidence such as behavioural changes and signs of injury, and, cameras must be placed in open areas of the flat and not in bedrooms or the toilet. 'If you have a good reason to suspect that your child is being harmed, then secret filming is allowed,' he said. 'But if you do it for no good reason and just want to check up on your maid . . . that would be an invasion of privacy.' Mr Lau's comments came after privacy concerns were raised last week by union leaders over the arrest of a 29-year-old overseas maid who was filmed allegedly physically abusing a nine-month-old boy under her care. She was released on $2,000 bail and will report to police on Sunday. The director of the Mission for Filipino Migrant Workers, Cynthia Tellez, agreed there was a need to monitor abusive maids but she said it was best to take preventive action. 'Talk to the person concerned and take preventive measures,' she said. 'If you put up a camera, there is no trust - and that's impractical in a domestic situation. 'If you do use a camera, make sure you have sufficient evidence [such as] injury marks.' Mr Lau said a draft code of practice on workplace surveillance would be released for public consultation next year. The code would cover both domestic maids as well as office workers and their right to privacy in personal communication, such as e-mail messages and telephone calls. Secret filming of maids has become increasingly common. In May last year, Suboto Anissa, 21, was jailed for two months after a hidden video camera captured her beating a two-year-old boy. It was the first jail sentence for a domestic worker accused of child abuse. Another maid, 37, was sacked after hidden films allegedly showed her abusing a 15-month-old boy last August. The Law Reform Commission recommended last year that the Privacy Commissioner look into issues relating to bosses who spy on their workers.