Thousands of nurses across NSW have gone on strike for 24 hours for the second time in 10 years, to pressure the state government to accept their demands for better pay and mandated nurse-to-patient ratios.

Nurses from up to 170 hospitals took part in a series of rallies on Thursday in Sydney, Albury, Bathurst, Broken Hill, Dubbo, Goulburn, Newcastle, Orange, Port Macquarie, Wagga Wagga, Wollongong and other areas.

A massive crowd of nurses and midwives carrying placards protested outside Parliament House, where the NSW Greens on Thursday introduced a bill to the upper house to legislate the union's preferred nurse-to-patient ratios.

"I went down into the city to let (Premier) Dominic Perrottet know that it's not safe in our hospitals," said Nichole Flegg, a midwife from Campbelltown who had finished three consecutive 12-hour shifts.

She said mothers of newborns were not getting the adequate care they needed, because of a shortage of midwives statewide compared to other states.

"You might have one midwife taking care of six to eight women and that's not even counting babies," she told AAP.

Thursday's industrial action comes more than a month after the NSW Nurses and Midwives' Association first voted in favour of statewide action that subsequently saw demonstrations at 150 public hospitals.

Nurses are demanding a nurse-to-patient ratio of one-to-four on hospital wards and a midwife-to-patient ratio of one-to-three, as well as a 4.75 per cent pay rise versus the 2.5 per cent a year allowed by the state government.

"Patients play Lotto depending which day they go to hospital," union General Secretary Brett Holmes told AAP.

"They could get lucky and get a properly staffed shift or they could get unlucky."

Following the February strike - the first by NSW nurses in a decade - Mr Perrottet said he hoped to provide a resolution but noted the issues were complex.

He also said Health Minister Brad Hazzard was in "constant dialogue" with the union.

For Debbie Ross, a clinical nurse in the Infection Control Department at Sydney Hospital with three decades of experience, she said burnout was affecting nurses who are unable to cope with the influx of patients.

"I'm just fed up and I'm angry. The system is broken," Ms Ross told AAP.

"We're on our knees. Nurses are falling like flies because COVID-19 is on the increase again. I've never seen so many nurses to walk away. We don't go in it for the money. It's a calling.

"When you take the ability to comfort or care patients, you're taking the essence of their work away."

Mr Holmes said the government had not extended an offer to the union since its last meeting with Mr Perrottet, who has been on paternity leave since March 17.

"Nurses and midwives are at breaking point," Greens health spokeswoman Cate Faehrmann said.

"It's time for the government to listen to their calls for safe nurse-to-patient ratios so that patients get a safe level of care."

Ms Faehrmann noted Queensland and Victoria had already legislated nurse-to-patient ratios and South Australia was considering the issue.

The union said life-preserving services were maintained at all public hospitals throughout the day.

The government had successfully argued to the industrial relations umpire the strike should not go ahead, but the union has defied the decision.

The latest strike comes after some NSW paramedics took industrial action on Tuesday with similar demands for improved resources and staffing.

On Monday, the paramedics union shared photos of ambulances queuing outside hospitals including Royal Prince Alfred, Wollongong, Wyong, John Hunter, Concord and others, waiting to offload patients at emergency departments.