Teachers and train drivers make up the majority of workers going on strike in the UK. They, among others, are seeking pay rises that would ease a cost-of-living crisis triggered by soaring inflation.
Large disruption to education and commuter travel is anticipated in the latest mass stoppages by public and private sector workers as the government and company bosses stand firm over wage demands.
The UK is set to see Wednesday the "biggest day of strike action since 2011", with up to 500,000 workers planning industrial action, according to umbrella group the Trades Union Congress (TUC).
Others on strike include border force workers carrying out immigration and customs checks at UK air and sea ports.
Britain has witnessed months of strikes from tens of thousands of workers — including also by postal staff, lawyers, nurses and employees in the retail sector — as UK inflation raced above 11 percent, the highest level in more than 40 years.
READ MORE: UK ministers to hold talks with unions amid hospital crises
'No magic wand'
"I would love, nothing would give me more pleasure than, to wave a magic wand and have all of you paid lots more," Prime Minister Rishi Sunak said Monday on a visit to public health workers, who are planning further walk-outs in the coming days and weeks.
"An important part of us getting a grip of inflation and halving it is making sure the government's responsible with its borrowing, because if that gets out of control that makes it worse and it's about making pay settlements reasonable and fair," Sunak added.
The latest official data shows 1.6 million working days were lost in the June-November period last year because of strikes –– the highest six-month total in more than three decades, according to the Office for National Statistics (ONS).
A total 467,000 working days were lost to walkouts in November alone, the highest level since 2011, the ONS added.
"I'll be working from home" Wednesday, charity worker Katie Webb, 23, told AFP. "I do support the strikes, the rail workers deserve better pay," she added.
Since late last year, a number of private-sector workers have managed to agree new pay deals with employers, leaving behind employees paid by the taxpayer.
"After years of brutal pay cuts, nurses, teachers and millions of other public servants have seen their living standards decimated –– and are set to face more pay misery," TUC General Secretary Paul Nowak said ahead of Wednesday's strikes.
READ MORE: Thousands of UK rail workers go on strike again
Nationwide rallies planned
Alongside the latest walkouts, unions are due to stage rallies Wednesday across the country in opposition to the Conservative government's plans to legislate against strike action by public sector workers.
Organised by the TUC, the nationwide protests will demand that "the right to strike is a fundamental British liberty", according to Nowak.
Sunak has introduced a draft law requiring some frontline workers to maintain a minimum level of service during walkouts.
The prime minister has defended the plans in parliament as "reasonable" and in line with other European countries.
In France on Tuesday, protesters launched a new push to pressure President Emmanuel Macron into dropping a pension reform plan, with hundreds of thousands taking to the streets and strikes disrupting transport and schools.