Very few firefighters are openly gay or lesbian, it is claimed
Fire brigades must do more to ensure gay and lesbian firefighters are not bullied or insulted at work, unions, ministers and equal rights groups say.
Campaign group Stonewall claimed staff had experienced name-calling and physical abuse and even had safety equipment tampered with as a joke.
And 25 UK brigades had not signed up to its diversity programme, it added.
Fire minister Sadiq Khan has written to fire chiefs urging them to "eradicate" homophobic behaviour.
The Fire Brigades Union estimates that just 0.5% of firefighters, less than 250, are openly lesbian, gay or transsexual.
Pat Carberry, secretary of the FBU's gay and lesbian committee, said those who came out as homosexual often faced mockery and intimidation.
Services often did not "know how to deal with" complaints, while one gay firefighter had committed suicide after facing discrimination and bullying at work.
Mr Carberry said: "When you are a firefighter, there are times when you have to concentrate totally on the job. If you don't you are putting yourself and your colleagues at risk.
"Traditionally, firefighters spend a lot of time sitting and talking and it is very hard to keep up a pretence about your personal life. If you are trying to hide something it is very stressful.
"That's something that could affect performance and endanger staff and the public."
Michelle Fullerton, manager of workforce programmes at Stonewall, said the fire service as a whole had scored 45% in its in its "equalities index". The police had done 15 points better with 60%.
Ms Fullerton said: "Homophobia is a real and current issue for the fire service. The big thing is the macho culture. If you are not seen to fit in with their attitudes then that gets noticed.
"That can get very serious. There have been instances of equipment being tampered with, even masks and breathing apparatus. These are terrifying things.
"If you can't trust colleagues, you compromise safety.
"But, as well as that really serious stuff, what seems to be happening is that people are still using insults like 'poof' and that kind of thing.
"It seems that making fun of lesbian and gay people, even while including them as part of the gang, is happening. That means you would look rather miserable if you didn't go along with the joke. It's a very strange sort of progress."
Some 31 of the UK's 56 brigades have signed up to Stonewall's Diversity Champions Programme.
Mr Khan's letter urges the rest to follow suit, saying bullying, harassment and discrimination on the grounds of sexuality have "no place" in the modern fire service.
It is essential to make brigades more diverse and recruit staff from the "widest pool of talent", it adds.
The letter has been countersigned by Stonewall, the FBU, the Local Government Association, the Chief Fire Officers' Association, Unison, the Asian Fire Service Association, the Fire Officers' Association, the GMB, the National Disabled Fire Association, Networking Women in the Fire Service and the Retained Firefighters Union.