Essex Fire and Rescue Service has been told it requires improvement across the board by inspectors - but has also been praised for emergency responses and tackling bullying.
The assessment came following a review by Her Majesty's Inspectorate of Constabulary and Fire and Rescue Services (HMICFRS).
Meanwhile, Suffolk Fire and Rescue Service was rated as good in a similar review.
The review assessed how effective each service is at preventing, protecting against and responding to fire and other risks; whether it provides value for money; how well it looks after its people and ensures fairness and diversity.
Essex was praised for its response to emergency calls but amongst the findings was "unacceptable" levels of bullying among staff despite "commendable" work by a new chief fire officer and her team.
In her report, Inspector Zoe Billingham said: "We found a very mixed picture - but within this there are good areas of performance.
"Importantly the service is good at responding to emergencies, and to national risks.
"Response times are in line with other significantly rural services and the service works well with other fire services and agencies to deal with major incidents.
"However, the way Essex County FRS manages fire prevention and protection is a concern.
"The new leadership team in Essex County FRS inherited a very poor cultural legacy with unacceptable levels of bullying and pockets of toxic behaviours.
"Much commendable work has been done by the new chief fire officer and her team, supported by the police, fire and crime commissioner, to address these deep-seated issues. But cultural transformation will take time."
WATCH: Essex Chief Fire Officer Jo Turton responds to the HMICFRS report
Essex Chief Fire Officer Jo Turton said the service welcomed the report.
"For us, there are no surprises in these findings; the feedback echoes what we told the inspectorate, and reassures us that we are self-aware and that our focus is in the right areas," she said.
"We know that our public wants to feel reassured that, when there is an incident, Essex County Fire and Rescue Service will respond quickly and effectively. I was pleased that the inspection recognised us as good in this area.
"As an organisation, we have been through some major changes in the last few years, but one thing that has remained constant is the dedication that our staff display.
"I want to reassure colleagues and public, that the safety of our own people and our residents remains the top priority for our Fire and Rescue Service.
"Culturally, we know there is still more to be done. Many improvements have been made, and the well-being of our people continues to be a personal priority of mine."
Roger Hirst, Police, Fire and Crime Commissioner for Essex, said the report confirmed the good progress that been made within the service since 2017.
"Importantly they have recognised the service is good at responding to fires and emergencies and responding to national risks. This is a reflection of the service's hard work," he said.
"The report will help us focus on areas where we still have more to do in particular around protection especially technical fire safety, prevention and above all getting the culture of the service to where it needs to be.
"We will continue to invest in the areas that require improvement and that we have already recognised as priorities within the Fire and Rescue Plan."
In the Suffolk report, the county's fire service were praised for keeping people safe from fire and other risks.
The result was said to be "testament to the hard work of the service" by the inspector who added that the service still needed to improve in its approach to fire prevention.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here