A report by His Majesty’s Inspectorate of Constabulary and Fire and Rescue Services said fire engine availability in the county had decreased, that the workforce was not used enough and that more effort was needed to improve brigade diversity.
It added that improvement was required to keep "people safe and secure from fire and other risks" and in looking after its own employees.
In response Chief Fire Officer Rob Barber insisted in the service's latest Statement of Assurance that he took the criticisms "very seriously" and that some issues such as recruiting more on-call firefighters were already being addressed.
Inspector of Fire and Rescue Services Wendy Williams stated: "The service is good at how it identifies risks in its communities and puts appropriate measures in place to mitigate those risks. And it is good at how it identifies those people in its communities who are most at risk from fire and works with its partners to good effect to reduce this risk.
"The service also has good financial management and collaboration arrangements in place.
"But there are some behaviours in the service which are not in line with the service’s values which is having a detrimental effect on staff. And the service isn’t sufficiently prioritising work to improve inclusion and diversity.
"Response standards and the availability of its fire engines have got worse and the service isn’t sure it has identified all its high-risk premises."
"Overall, while there are some good aspects of the performance of Staffordshire Fire and Rescue Service, there are a number of areas where performance has declined since the last inspection and I expect to see progress made against these. We will continue to monitor progress through our usual monitoring arrangements," she added.
Mr Barber stated: "I would like to reassure you that I take these areas very seriously and I am confident that we can address them, many of these have already moved forward significantly since the inspection last autumn.
"One particular area where I would welcome support from our local communities is in relation to on-call firefighters. Our recruitment campaign has been running for over a year now, but we are still struggling to recruit people, despite it being a paid role.
"Our on-call firefighters come from a range of backgrounds, most have the role as secondary employment although for some it is their main job. We would encourage people who may never have thought about if before to consider joining us, as on-call firefighters really are vital to our local communities."
A recruitment drive for on-call staff is underway in Abbots Bromley near Rugeley.
The service attended more than 8,400 incidents in the last year, with 726 of those incidents being road traffic collisions. There was a 15 per cent decrease in accidental house fires and a 25 per cent increase in such injuries.