Hundreds of nurses and midwives at a public hospital run by a private conglomerate under the spotlight of an inquiry, are walking out for more than 24 hours calling for better pay and conditions.

Striking staff on Monday at Northern Beaches Hospital in Sydney are demanding a one-off 15 per cent salary increase, 30 per cent night-shift penalties, improved leave entitlements and mandated nurse to patient ratios.

The 488-bed hospital, which opened in 2018 to replace two smaller public hospitals, is one of 38 Australian hospitals run by Canadian-controlled Healthscope, owned by a multi-national private investment fund.

The controversial public-private partnership was set up under the former coalition state government.

The NSW Nurses and Midwives' Association is urging the "second-largest private operator to put patients and staff before profits and implement safe working conditions... so they can provide quality patient care."

The strike action comes weeks after a parliamentary inquiry was established after the death of two-year-old toddler Joe Massa.

He and his parents waited three hours in the emergency department at the hospital in September 2024.

His heart attack - caused by significant fluid loss - followed repeated failures by hospital staff to conduct basic observations or respond to concerns of his mother.

The union says life-preserving care and minimum staffing levels will be maintained throughout the stop-work actions.

AAP has aproached Healthscope for a comment.