More than 400,000 health workers will be balloted for strike action, threatening a massive escalation of industrial unrest across the country as disputes over issues such as pay grow.
Unison has announced that its members in England, Wales and Northern Ireland, ranging from nurses and ambulance crews to hospital porters and cleaners, will vote in the coming weeks on whether to launch a strike campaign.
Here is everything you need to know about it.
Why are they considering striking?
Unison general secretary Christina McAnea said the Government’s decision to award a £1,400 pay increase in the summer had sparked outrage among NHS employees, resulting in resignations across the service.
She accused the Westminster Government of treating unions as the "enemy within" and ignoring calls to negotiate pay in order to avoid industrial action.
“They don’t want to talk to us – they want to demonise us,” she said. “The NHS is haemorrhaging staff and cannot recruit new employees, partly because pay is so low.”
McAnea said that due to staff shortages, NHS employees are being asked to work double shifts or extra hours on weekends, leaving them "exhausted."
NHS workers across England went on strike over pay in 2014. Prior to that, the last UK-wide strike involving health workers occurred in 1982.
How could potential strikes affect Christmas?
Almost a million NHS employees could go on strike or take other forms of industrial action before Christmas.
McAnea said that there would be so-called "life and limb" coverage if there is a strike, but said that many hospitals are already operating at such staffing levels due to the NHS’s recruitment crisis.
She predicted that any strike action from Unison could be coordinated with other health unions, threatening the largest strike in years, and added that she cannot guarantee that services would not be disrupted.
“Many of our members feel they are already operating at strike levels of staffing,” she said. “If they go on strike they hope it will show the Government how bad things have got.”
The Unison leader said the public had supported railway workers’ strikes, and she is confident that nurses and other health workers will receive similar support.
When will Unison members start voting?
Unison members will begin voting on Thursday 27 October.
What other health worker strikes may take place?
More than 15,000 ambulance workers from 11 trusts in England and Wales will also this month vote on industrial action in pay disputes.
The voting for ambulance workers represented by the GMB union will begin on Monday 24 October, with the results expected at the end of November.
The union said that any strike action could occur before Christmas, and that its members have been angered by the Government’s 4% pay award, which it says will result in "another massive real-terms pay cut."
In Scotland, it was said that recent pay talks between the Scottish Government and unions representing NHS staff "did not make any progress."
Union representatives met with Health Secretary Humza Yousaf and Deputy First Minister John Swinney on 12 October amid the threat of winter strikes.
Yousaf told the PA news agency he would make a "significantly improved offer" to NHS workers in order to avoid walkouts, but Wilma Brown, chairwoman of Unison’s health committee, said she had written to members urging them to support strike action, adding, “We are disappointed that talks did not make any progress yesterday and that we are still so far apart.”
The Royal College of Nursing (RCN) also said that during the meeting, no significantly improved offer was made. The union is asking all of its UK members if they are willing to walk out over pay for the first time in its 106-year history. That ballot closes on Wednesdsay 2 November.