The Government is facing a fresh wave of strikes in the new year by health workers, including ambulance staff, amid an escalation of a bitter dispute over pay.
Unison and Unite announced that their NHS members in England will walk out for 12 hours from 9am on January 29, and again for 24 hours on February 24 - while ambulance workers in the GMB union in England and Northern Ireland will strike on January 29 and 30.
NHS staff will also launch a work to rule between January 30 and February 24, including refusing to do unpaid overtime and making sure they take their breaks.
Unions said it had ruled out industrial action over Christmas as services were at "breaking point", but with no end to the deadlock, the dispute could now continue up to the general election in May.
The Health Department repeated that 10,000 jobs would be at risk if the pay award was given in full.
The dispute flared earlier this year after the Government decided not to accept a recommended 1% pay rise for all NHS staff.
Health workers from 12 unions, including nurses and midwives, took strike action in October and November - many for the first time in their lives.
Unison said the third round of industrial action next month was part of a continued protest at the Government's decision to reject a 1% pay rise for NHS staff which was recommended by the independent Pay Review Body in 2014, and the fact most health workers will not receive a pay increase in 2015/16.
Christina McAnea, Unison's head of health, said: "We warned months ago that this dispute is here to stay unless the Government and NHS employers are prepared to negotiate with us.
"Today is likely to be the busiest day in the NHS with ambulance and A&E staff put under huge pressure to deal with the fallout from the many Christmas parties taking place across the country.
"We have decided not to take strike action over the Christmas period as services are already at breaking point at this time. Our members are demonstrating their concern for patient safety. I only wish the employers and Government would do the same.
"Instead, they are being completely irresponsible by refusing to have meaningful negotiations on how we resolve this dispute, and they are putting patients lives at risk.
"Our members' pay has been frozen or held down for the past five years and there is no end in sight. On average, they have lost around 10% in the value of their pay over the life of this parliament.
"We now have no option but to escalate and plan for longer strikes. The anger among health workers has reached levels where they are now ready to walk out for 24 hours. NHS staff have been singled out by this coalition government for the worst treatment across the public sector.
"Other groups will get their recommended pay increases - for MPs this is 11%.
"It is a national disgrace that 77,000 NHS staff still don't receive the Living Wage and that many have to rely on food banks. The governments in Wales and Scotland have committed to paying this."
Rehana Azam, national officer of the GMB, said: "It is regrettable that GMB has no alternative but to escalate the strike action in the NHS.
"The Secretary of State for Health, Jeremy Hunt, is acting irresponsibly with a continued entrenched position by not engaging in any meaningful talks with the health unions."
Steve Rice, who chairs the GMB's ambulance section, added: "I have worked for the ambulance service for almost four decades and, in this time, I have worked under 17 secretaries of state for health.
"Never have I experienced staff morale at such a breaking point."
Rachael Maskell, head of health at Unite, said: "Patient safety is our members' number one priority which is why they won't be taking action over the Christmas and new year period. But the government's continued refusal to negotiate on pay has left NHS staff with no option but to step up their fight with more strike action in the new year."
A Department of Health spokesperson said: "This is disappointing. NHS staff are our greatest asset and we want to make the current pay system fairer, which is why we have put forward proposals that would guarantee all staff would get at least a 1% pay rise this year and next, but these have been rejected by the unions.
"We have taken tough decisions to increase the NHS budget, but we can't afford a consolidated pay rise in addition to increments without risking 10,000 frontline jobs."
Danny Mortimer, chief executive of the NHS Employers organisation, said: "NHS staff have received either an increment (worth around 3.4%) or a 1% pay award this year. Employers are, of course, disappointed that a number of trade unions will again seek to disrupt the delivery of care, impacting on patients and their families as well as their colleagues.
"This is one of the busiest periods for the NHS. We hope that trade union members will maintain their previous constructive approach, so that the most urgent patients continue to receive the care and treatment they need.
"Discussions continue with trade unions regarding pay, though agreement has, we acknowledge, been difficult to reach. Employers continue to be clear that they cannot afford further increases in pay at this time.
"A pay award for all staff on top of increments would have cost the equivalent of 14,000 newly-qualified nurses, which could have put further pressure on the health service and staff as they strive to give safe, quality patient care."