Nurses and midwives will walk off the job for 24-hours on Wednesday in the fourth such action this year over staffing and pay issues

Rallies will be held across the state including Sydney's CBD, where union members will march along Macquarie Street from Hyde Park towards state parliament.

It comes as the latest COVID wave places even more pressure on the health system.

NSW Nurses and Midwives' Association (NSWNMA) general secretary, Shaye Candish said staff were "incredibly burnt out" and at risk of abandoning the NSW health system for other states where conditions are better.

The NSWNMA is calling for mandated nurse-to-patient ratios which have been implemented in several Australian states with broadly positive results.

"Nurses and midwives continue to turn up to work being understaffed and completely overstretched which means that they're not able to deliver the care that their community deserve," Ms Candish said.

"States like Queensland and Victoria are actively encouraging NSW nurses and midwives to go and work interstate because they have provisions like ratios."

Ms Candish said the government remains hesitant to commit to ratios as a solution, despite talks being held with NSW Health Minister Brad Hazzard, senior health department officials and the union.

Mr Hazzard has been contacted for comment.