Firefighters and control room staff have voted overwhelmingly to strike in a dispute over pay.
Members of the Fire Brigades Union (FBU) backed walkouts by 88% on a huge turnout of 73% after earlier rejecting a 5% pay offer.
The union said it was giving the government and employers 10 days to make an improved offer before deciding its next move.
If they go ahead, the strikes will be the first nationwide fire strikes over pay since 2003.
The announcement came as up to half a million teachers, civil servants and rail workers prepare to stage a day of mass industrial action on Wednesday.
Nurses and ambulance workers are also continuing to stage a series of walkouts in their own dispute over pay and conditions.
FBU members rejected the below-inflation 5% pay offer last November.
The union said the vote on industrial action follows more than a decade of real-terms pay cuts.
Polling shows public support for strike action by firefighters is strong, with three in five people backing action, said the union.
General secretary Matt Wrack said: “Firefighters across the UK have spoken. The Fire Brigades Union has a decisive mandate for strike action.
“This is an overwhelming vote for strike action against an offer which would mean further significant cuts to real-terms wages for firefighters and control room staff.
“They have already lost at least 12% of the value of their pay since 2010.
“This is an absolute last resort for our members. The responsibility for any disruption to services lies squarely with fire service employers and government ministers.
“Rishi Sunak’s government has refused to make funding available for a decent pay offer to firefighters and control staff.
“Firefighters were among Britain’s Covid heroes who kept frontline services going during the pandemic. The prime minister has badly misjudged the public mood by imposing pay cuts on key workers.
“Our members risk their health and safety, and sometimes their lives, round the clock to keep people safe and serve their communities.
“However, with inflation and energy bills rocketing, they are now increasingly struggling to pay the bills or to afford the basics.
“The government and the employers have the power to stop strikes from happening by making a credible offer that can resolve this dispute. The ball is in their court.
“We have delayed calling strikes to allow the employers to meet us and to make a new offer. I hope they take that opportunity.
“Otherwise, in the coming weeks, we intend to announce a series of strike dates and industrial action.”
Shadow home secretary Yvette Cooper said: “Firefighters run towards danger when the rest of us run away. They put their lives and their health at risk to rescue others and they need fair pay and conditions.
“No one, including firefighters themselves, wants a strike. It is this Conservative government’s reckless behaviour that has crashed the economy, and their failure to get a grip on inflation means working people are struggling more and more. This is their mess to fix.
“It’s up to the home secretary to get around the table and talk. She should be doing everything she possibly can to negotiate a deal and prevent a strike.”