Nursing staff from more than 55 NHS trusts in England are taking part in industrial action on Wednesday and Thursday following two days of action in December.

The Royal College of Nursing (RCN) has announced that two further, bigger strikes will be held next month, while the GMB union is expected to announce further ambulance worker strike dates on Wednesday afternoon.

Pat Cullen, chief executive and general secretary of the RCN, said nurses felt “totally heartbroken” going on strike, but felt they had no choice.

She told ITV’s Good Morning Britain the NHS was not currently delivering an acceptable minimum staffing level, which “flies in the face” of new anti-strike laws calling for minimum service cover on strike days.

“Minimum staffing levels are not available for our patients or our nurses on any day of the week,” she said.

“So to try and suggest that we’re going to have minimum staffing levels on days of industrial action is just so far removed from reality, and in fact it is a total insult to our patients and to nurses – it just doesn’t happen.

“You cannot have minimum staffing levels with 47,000 unfilled posts. So, I do not know how this Government’s going to do this.

“We have campaigned year on year for a minimum staffing level to be put in place – safe staffing legislation to protect our patients and to ensure that our brilliant nurses can do their jobs and continue to provide safe care and treatment, but they cannot continue to do that with 47,000 unfilled posts.”

She issued a warning to the Government that more strikes are on the cards, as immigration minister Robert Jenrick did not rule out nurses continuing to strike for months.

Ms Cullen said: “I would say to the Prime Minister this morning: If you want to continue to have strikes, then the voice of nursing will continue to speak up on behalf of their patients and that’s exactly what you will get.”

She said staff “are working in a crisis every single minute of the day”, adding that ignoring that was “living in a parallel universe”.

Ms Cullen added: “We will only recruit and retain our nurses if we pay them a decent wage so that they can continue to work in the health service and not have to leave to other jobs that will give them two or three pounds an hour more so they can pay their bills.”

She said there were no further talks currently planned with the Health Secretary Steve Barclay.

Asked if “inflationary pay deals” would end up taking money out of the NHS, as Mr Barclay has said, she told BBC Radio 4’s Today programme: “We can either have our focus totally on balancing the books or we can continue to respect and treat this NHS as it should be for every single patient right throughout the country.

“So, we have to address the crisis within the NHS, you will only do that by paying nurses a decent wage and filling the 47,000 unfilled posts…”

Writing in the Independent, Mr Barclay said that, while he recognises the cost-of-living pressures on NHS staff, “unaffordable pay rises” will stoke inflation.

He said: “If we provide unaffordable pay rises to NHS staff, we will take billions of pounds away from where we need it most. Unaffordable pay hikes will mean cutting patient care and stoking the inflation that would make us all poorer.”

The Health Secretary insisted there is “much common ground” between both sides of the dispute, stating that ministers “want to work with union leaders to improve the NHS and deliver better care” and that a “fair way” to a resolution can be found.

On Tuesday, Mr Barclay signalled that pay negotiations will look ahead to next year rather than reflecting on the 2022/23 pay award, which unions have said must be reviewed.

He said: “I have had constructive talks with the Royal College of Nursing and other unions about the 2023/24 pay process and look forward to continuing that dialogue.”

As the strikes get under way, the NHS is reminding patients to attend all their usual appointments unless they have been contacted, and to seek urgent care if needed during the strikes.

NHS England said patients should use services “wisely” by going to NHS 111 online but continuing to call 999 in a life-threatening emergency.

Thousands of operations and appointments are expected to be cancelled during the two consecutive days of strike action. Almost 30,000 needed to be rescheduled following December’s nurse strikes.

The health service is likely to run a bank holiday-style service in many areas.

The RCN has agreed to staff chemotherapy, emergency cancer services, dialysis, critical care units, neonatal and paediatric intensive care.

Some areas of mental health and learning disability and autism services are also exempt from the strike, while trusts will be told they can request staffing for specific clinical needs.

When it comes to adult A&E and urgent care, nurses will work Christmas Day-style rotas.

It comes after Matthew Taylor, chief executive of the NHS Confederation, urged ministers to renew pay talks with unions in a bid to halt further industrial action.

In comments shared exclusively with the PA news agency, Mr Taylor said the NHS is trapped in a vicious cycle brought about by extreme pressures in emergency care, ongoing high levels of flu, Covid and respiratory infections, plus industrial action.

He said if “there is no realistic prospect of a solution, then we’re facing the prolonged war of attrition between the Government and the unions that we’ve been fearing”.

Mr Taylor added: “Ahead of the next round of strikes, our message to the Government is to give the NHS a fighting chance and do all you can to bring an end to this damaging dispute.

“The Prime Minister must not allow the stand-off in the wider public sector to hold back a deal being reached in the NHS.”

The RCN has been calling for a pay rise at 5% above inflation, though it has said it will accept a lower offer.

Officials from the Unite union will also meet later on Wednesday to decide whether to call fresh strikes among its ambulance members in England, Wales and Northern Ireland.

Meanwhile, Education Secretary Gillian Keegan is due to meet teaching union leaders on Wednesday in a bid to avert walkouts in February and March, which the NEU has said could affect more than 23,000 schools.

Immigration minister Robert Jenrick told Times Radio: “We would strongly encourage those head teachers to do everything that they can to keep their school open.

“Because as anyone who’s a parent knows, it’s extremely inconvenient when you can’t send your children to school and have to make alternative arrangements, and that has real world consequences.”