The Government is being urged to reach a compromise with unions and stop the NHS being "held hostage" between both sides after nursing leaders announced further strike dates in the new year.
The Royal College of Nursing (RCN) today said that unless negotiations are opened, its members will walk out on January 18 and 19 in an escalation of the pay dispute with the UK Government.
The action will take place at more NHS employers in England than happened this month, increasing from 44 to 55 trusts, said the RCN.
The RCN, which held two days of strike action in England, Northern Ireland, and Wales on December 15 and 20, said it has repeatedly invited ministers to hold talks on NHS pay.
But Prime Minister, Rishi Sunak, has insisted that refusing to negotiate on public sector pay is the "right thing" in the long term.
The new nurse strike dates come after Unison announced that its members at five ambulance services in England will walk out on January 11 and 23.
'Life and Limb'
Meanwhile, the planned post-Christmas strike on December 28 by ambulance workers in the GMB union has been suspended.
Matthew Taylor, chief executive of the NHS Confederation, said that while health leaders will be relieved by next week's strike being called off, trouble awaited in the new year.
He added: "No health leader wants to be in this situation and the new strikes announced for January could have been avoided had the Government attempted to find more common ground with the unions over pay.
"The Government cannot just sit back and let these strikes happen when patient care is on the line and the unions must honour their commitment to protect 'life and limb'.
"It's clear this is becoming critical and the worry is that the NHS will be held hostage to this position of stalemate between both sides.
"This benefits no-one and the Government must act and reach a compromise with trade unions now."
Mr Taylor said the strikes had already caused disruption, with 25,000 rescheduled procedures and "much longer" response times for ambulance calls.
But while the full effects of the strikes will not be known for some time, he added, there was already a rise in "walk-ins" to A&Es and delays in patients being discharged from hospital – potentially leading to local services being clogged up.
"The full effects of the strikes won’t be known for many days and weeks, but we are now starting to see the ramifications," Mr Taylor said.
"We are seeing an increase in 'walk-ins' to emergency departments and a slow-down in patients being discharged from hospital. Both will serve to clog up local services and lead to greater delays over the Christmas period.
"It's clear that the NHS is very fragile at the moment, and it doesn't take much to push it off kilter.
"That's why we continue our plea to the Prime Minister and trade unions to resume talks in order to avert planned and future strikes. Without a swift national resolution, patients will continue to suffer and that can't be allowed to happen."
RCN members will not be striking in Wales and Northern Ireland again in January, while in Scotland, RCN members this week overwhelmingly voted to reject a revised NHS pay offer from the Scottish Government.
Strike action had been paused pending the ballot's outcome, but the RCN Scotland will now announce dates for strike action early in the new year.
Government Continue to Refuse Pay Offer
RCN general secretary Pat Cullen said: "The Government had the opportunity to end this dispute before Christmas but instead they have chosen to push nursing staff out into the cold again in January. I do not wish to prolong this dispute but the Prime Minister has left us with no choice.
"The public support has been heart-warming and I am more convinced than ever that this is the right thing to do for patients and the future of the NHS.
"The voice of nursing will not be ignored. Staff shortages and low pay make patient care unsafe – the sooner ministers come to the negotiating table, the sooner this can be resolved. I will not dig in, if they don't dig in."
Ms Cullen has said the union's demand for a 19% rise – dismissed by ministers as "unaffordable" – is simply a "starting point" and that she would put any new offer to her members.
But despite some Tories calling for a rethink the Government has repeatedly refused to stray from the advice of the independent pay review body for a £1,400 raise, which is estimated to be an average of a 4.3% raise for qualified staff.
Saffron Cordery, interim chief executive at NHS Providers, said: "We understand how nurses and ambulance staff feel, and how they have reached this point.
"Below-inflation pay awards, the cost-of-living crisis, severe staff shortages and ever-increasing workloads make for near-impossible conditions.
"It's deeply concerning that escalated and prolonged action is set to unfold in January. Serious talks, including specifically on pay, need to take place between health ministers and unions without delay."
Mr Barclay said: "While union members will not be going ahead with strikes over Christmas, we are disappointed they have announced further co-ordinated strikes in January to cause maximum disruption at a time when the NHS is already under extreme pressure.
"Ambulance staff on picket lines have been raising concerns about working conditions and handover times, so it is important to use this extra time to keep talking about how we can make the NHS a better place to work. However, the unaffordable pay demands of unions would mean taking money away from frontline services and cause further delays to care.
"Strikes are in no one's best interest, least of all patients, and I urge unions to reconsider further industrial action to avoid an even greater impact on patients."
This article contains information from PA Media.