The Fire Brigades Union has lambasted the “appalling cuts” to fire services across the country, which it says are putting public safety at risk.
In the West Yorkshire Fire and Rescue Service, the number of full-time equivalent firefighters fell from 1,609 in 2010 to 1,027 in 2018 - a drop of 36 per cent.
This is one of the biggest cuts in any fire and rescue service in England.
At the same time, crews took more than a minute longer to respond to callouts in the 12 months to March 2018 than in the same period in 2010 - a 14 per cent increase, bringing the total response time to 8 minutes 28 seconds.
The figures refer to primary incidents, which are the most serious fires with potential to harm people or cause damage to property.
Across England, the number of firefighters has fallen by more than 22 per cent since 2010, from 41,632 to 32,340, and there are now 45 fewer fire stations.
The average time taken to respond to serious incidents increased by more than 30 seconds over the same period.
The Home Office said local factors could affect response times, and that there is not a straightforward link between response times and the outcomes of a fire.
However, Matt Wrack, FBU general secretary, said there was a clear link between slower response times and government cuts.
“Year on year we are seeing appalling cuts to the service and these figures are clear evidence that the cuts have gone too far,” he said.
“Understaffed fire stations across the country struggle to provide a 24-hour service to their community, with the starkest effect outside of cities.
“Fire and rescue services are expected to do more with less and it is only down to the dedication of fire and rescue staff that the service is performing at all.
“The service is at breaking point. Public safety is being put at risk.”
Response times in West Yorkshire are quicker than the England average, which last year stood at 8 minutes 45 seconds.
The slowing responses in England have come despite the fact that firefighters are attending fewer primary incidents.
In 2009-2010, there were 3,516 in the West Yorkshire area, compared to 2,665 by 2017-18.
There has also been a fall in the number of fire stations operated by the service, from 48 in 2010 to 40 in 2018.
A Home Office spokesperson said: “The government is thankful for the continued tireless efforts of firefighters across the country.
“There has also been a long term downward trend in both fires and fire deaths for many years, recently reaching historically low levels, and we are confident that fire and rescue services have the resources they need to do their important work.”