Doctors and nurses at a major Sydney hospital failed to properly wash their hands when no one was watching, risking patients' lives, a new study found.

Researchers from University of NSW found the staff's hand-washing compliance rate dropped from 94 per cent to 30 per cent when human auditors stopped monitoring their behaviour and automated surveillance kicked in.

Hand hygiene is important for infection control. Credit:Michele Mossop

They are calling for an overhaul of the auditing system, which may still require human auditors because automated surveillance and reminder technology are expensive, and the re-education of hospital workers about the importance of hygiene.

"Hand hygiene is the keystone to infection control that prevents healthcare workers from being colonised with a potentially life-threatening disease; that reduces hospital-acquired bloodstream infections that can kill up to 20 to 30 per cent of patients," lead author Mary-Louise McLaws said.