Firefighters in the West of England fear hostility, resistance and antisocial behaviour on the doorstep if they have closer links to the police.

The Avon branch of the Fire Brigades Union says crews are seen as impartial and trusted, and the public must be "in no doubt as to who does what".

The warning came in response to police and crime commissioner Sue Mountstevens' bid to join the Avon Fire Authority.

Ms Mountstevens said she wants to bring her nine years' experience to the table to help it deliver an effective and efficient fire service.

In a letter to the AFA, Avon FBU secretary Gary Spindler said: "The role of fire fighters is built on trust, not only between ourselves when at incidents but also between ourselves and the communities we serve.

"Firefighters and police have completely different roles in society. We must ensure the public are in no doubt as to who does what.

"If there's a continued narrowing of perceptions of separation between the two services it's certain that the downside will be the perceived removal of our impartiality in place of law enforcement.

"The issue with the blurring of roles increases the risk to our members and the communities themselves. We believe there will be more guarded responses on the doorstep, with vulnerable groups denying access because of the association with the police.

"There may well be a reluctance to discuss fire safety because of the perceived possible police involvement.

"There may be an increase in antisocial behaviour towards firefighters, both in peacetime and times of social tension.

"It may become more difficult to retain from underrepresented communities if there's a perceived increase in police association with the fire service.

"We're struggling to find benefits that would balance this out."

If she is allowed to join, Ms Mountstevens, the PCC for Avon and Somerset, would be given full voting rights and able to send a representative if she could not attend a meeting.

In May, AFA members deferred their decision amid uncertainty over the benefits she would bring, and last week delayed again after the Home Office failed to respond to their questions.

Ms Mountstevens is already a member of the fire authority for Devon and Somerset.

She said: "I already hold the chief constable to account, set the council tax precept and ensure the police are delivering an efficient and effective service to local people.

"I intend to contribute such knowledge and help to Avon Fire Authority to help them deliver an effective and efficient fire service for the area."

She said firefighters already work closely with the police but "by being part of Avon Fire Authority there is an opportunity to share best practices and further scrutinise such collaboration in an open forum to ensure partnership working is continuously being improved to benefit our communities".