Tens of thousands of public sector workers are returning to work following the biggest walkout in a generation which brought disruption to schools, hospitals and other key services across Britain.
Unions hailed Wednesday's "historic" strike as the biggest since the 1979 Winter of Discontent, saying up to two million workers took industrial action over the Government's controversial pension reforms.
But David Cameron said the "irresponsible and damaging" walkout had been a "damp squib" and was not as well supported as claimed.
The strike closed more than three quarters of schools in England, as well as courts, museums, libraries and jobcentres, disrupted transport, hospitals and government departments and led to around 15% of driving tests being cancelled.
In the capital, police were called in to help the London Ambulance Service (LAS) attend emergencies after thousands of NHS workers went on strike. Officials from LAS said it faced "severe pressure" after 42% of staff walked out, while NHS London strategic health authority said the service received 30% more 999 calls than normal.
More than 1,000 rallies were held across the UK, including one in central London attended by tens of thousands of workers, some accompanied by their children.
Len McCluskey, leader of Unite, said the rally showed the depth of anger among public sector workers, while Unison leader Dave Prentis hit back at Mr Cameron's comments.
"I wouldn't call two million people taking strike action a damp squib," he said. "The thousands of picket lines, demonstrations, rallies and events are not a figment of our imagination. These people are angry public servants who the Government has driven to the end of their tether."
Cabinet Office minister Francis Maude described the action as "inappropriate, untimely and irresponsible" and said that union leaders should take full responsibility for the disruption.
He also branded claims the Government is not negotiating with unions as "simply not true" and said that formal discussion with teaching unions would take place on Thursday and meetings with health union leaders would be held on Friday.