Landmark legislation to prevent employers from spying on employees will come into force in NSW at the beginning of October.

NSW will become the first Australian state to outlaw unauthorised surveillance of employees using technologies including video cameras, e-mail and tracking devices.

The Workplace Surveillance Bill 2005, which was passed by the Upper House in June, makes it a criminal offence to take part in any form of covert surveillance unless an employer can prove to a magistrate it has reasonable suspicion of wrongdoing.

The legislation replaces the Workplace Video Surveillance Act 1998, and extends the scope of the law to e-mail and tracking devices such as GPS in cars and even potentially to building swipe cards.

NSW Attorney General Bob Debus has said the new laws are necessary to protect workers from unscrupulous employers snooping into private e-mails or telephone calls.

Business lobby group Australian Business Limited has recommended all businesses undergo an audit of current surveillance activities and devise an Internet and computer usage policy.