Fire safety checks across England have fallen by 42% over the last seven years, according to the new watchdog for fire and rescue services.
HM Inspectorate of Constabulary, Fire and Rescue Services says brigades do a good job in emergencies, but amid cuts have reduced "vital" prevention work.
Avon was rated "inadequate" in its fire regulation work.
The Home Office said it wanted services to take "urgent action" where any failings had been identified.
Of the 14 mainly rural services that have been inspected so far, eight others were told to improve checks.
The services requiring improvement in their safety checks were: Bedfordshire, Cornwall, Hampshire, Isles of Scilly, Isle of Wight, Lincolnshire, Surrey and Warwickshire.
The other fire services inspected were all rated "good" for their safety audits. They were Cambridgeshire, Cheshire, Herefordshire and Worcester, Hertfordshire, and Lancashire.
The watchdog praised what it described as the heroic rescues firefighters carry out - highlighting the efforts at the Grenfell Tower fire as an example - but said the number of buildings given safety checks has been falling steadily.
Firefighters are supposed to look for hazards such as blocked fire exits or faulty doors and give notice to building owners of improvements which are needed.
Inspector Zoe Billingham said fire services might simply not know what risks existed in their local areas and that reduced safety.
She said: "A vital part of a fire and rescue service's role is to ensure that premises are being kept safe, but protection work is not a priority currently."
She added that the services all have different definitions of "high risk" buildings which are necessary to inspect, making it hard to draw direct comparisons.
The watchdog said the number of audits carried out by firefighters dropped from 84,575 in 2010-11 to 49,423 in 2017-18.
'Fundamental culture services'
"The consequences of long-term under-investment in this critical area are too often evident," the report said. "Protection teams are not given a sufficiently large share of the service's resource to do their work."
The inspectorate also criticised the culture of the 14 services inspected - a quarter of staff said they had suffered bullying in the last 12 months, and some had no dedicated provision for female firefighters to change or shower.
Ms Billingham said: "We were also concerned to find fundamental cultural problems in too many services.
"Too often these outdated practices are not occurring under the radar - most worryingly they are seen as the norm. Swift and sustained action is required for fire and rescue services to create a modern, inclusive environment, where everyone feels welcome."
The Fire Brigades Union said working conditions for firefighters still needed to improve and it was "outrageous" to find that facilities for some female staff are lacking.
On the drop in safety checks, FBU general secretary Matt Wrack said: "Services are overstretched and under-resourced, and unable to fulfil key parts of their remit.
"Ministers must urgently invest in the fire and rescue service, and in particular in fire safety resources, to ensure that the public are kept safe."
A Home Office spokeswoman said: "We are pleased most of the services were judged to be effective at keeping people safe from fire and other risks.
"However, we are extremely disappointed that HMICFRS found that some services require improvement in how they look after their staff and raised concerns about how some carry out their protection duties.
"We expect fire and rescue services to take urgent action to address these failings and will be engaging with the sector on next steps."
Avon Fire and Rescue Service was rated inadequate on both safety audits and "promoting the right values and culture", while in other areas it was said to be "good" or "requiring improvement".
Avon Fire Authority said the HMICFRS assessment represented a "further challenge" but the "report findings reflect what we already know and are working on".