The Buckinghamshire Fire and Rescue Service workforce has shrunk down by more than a third since 2010, new data reveals.
The Fire Brigades Union, which collected the data, said firefighters are being asked to do more with less.
Freedom of information requests by the union show there were 369 people employed by the Bucks Fire and Rescue Service this year, including full-time and on-call fire fighters and other supporting staff, such as call handlers.
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It was 256 fewer staff than the workforce of 625 in 2010. It meant the number of jobs fell by 41%, the biggest fall seen across the UK's fire and rescue services.
Across the 49 fire and rescue services to provide data, the number of firefighter jobs has fallen by 21% in the UK over the last 14 years.
England was the worst impacted, with 10,000 jobs cut – down 22%.
In the same period, Scotland lost 1,400 firefighters, Northern Ireland lost over 200, and Wales lost 500.
Matt Wrack, FBU general secretary, said: "Fourteen years of austerity have devastated the fire and rescue service. Every region has been hit, with 12,000 firefighters lost to cuts across the UK."
He added the rise in flooding, wildfires and storms due to the climate emergency, means firefighters are "being asked to do more with less".
He said: "999 response times are slower than ever before, putting homes and lives at risk.
"To protect the public, Labour must invest in the fire and rescue service as a matter of urgency."
The figures also show a dozen fire and rescue services in England lost a quarter or more of their workforce.
The FBU has also found that 4,000 firefighters have both a full time and an on-call contract, meaning that they will be counted as two firefighters in the data.
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A Home Office spokesperson said: "Throughout the country, our firefighters operate in uniquely challenging and high-risk environments, constantly going above and beyond the call of duty to protect our communities".
They added: "We will continue to work closely with stakeholders across the sector to ensure all services have the resources they need to protect communities at the highest standard."
Fire and rescue services have received around £2.87 billion this financial year, they said.
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