Firefighting members of a national union said they did not know whether strike contingency plans were sufficient after response times in Northamptonshire increased by more than a third during industrial action last year.
Northamptonshire Fire Service revealed statistics which showed that average response times during strike action during November and December last year were, on average, more than three minutes longer than usual.
While fire crews usually arrive within eight minutes and 24 seconds of receiving a call, the average time was 11 minutes and 30 seconds during those periods.
One member of the Fire Brigades Union (FBU) said that staff did not know whether plans during ongoing strikes would be enough to cover the service.
During a 24-hour strike by fire crews this week, Benjamin Muddle, FBU representative for Northamptonshire, said: “There are contingency plans to cover the county for the full 24-hour period.
“However, last time response times nearly doubled in some cases so we don’t know if it will be enough now.”
Northamptonshire Fire Service confirmed they had improved by keeping two more stations open than during last year’s strikes.
Aspokeswoman said: “We’ve reviewed our plans and we believe that our latest arrangements will enhance potential response times during peak shifts.
“This will include keeping two extra county stations open at night time.
“We usually have 24 officers on duty per shift and still have 17-19 during strikes.”
Martyn Emberson, chief fire officer for Northamptonshire added: “Our robust contingency measures are some of the best in the country and they are getting better.”
The FBU strikes are taking place in response to government pension reforms due to become law in April.
These will see staff facing the possibility of a reduced pension if they cannot match the same fitness levels at 60, as their 20-year-old colleagues.