A former firefighter who worked in the team responsible for changing London Fire Brigade's (LFB) culture has said he has "no faith" in the brigade's ability to reform.
Gareth Dawes, 40, also warned against black and women Londoners joining the brigade.
Last week a damning independent review into LFB found it "institutionally misogynist and racist".
Fire commissioner Andy Roe has said "change has started now".
Mr Dawes worked in the cultural change team at the brigade's headquarters in Union Street, Southwark, for five months, until September 2021. He had been invited to join the team after detailing his experiences of racism within the organisation.
But once there he found a culture that was "way more toxic than anything I'd experienced at station level".
"What's really sad is that I was brought into a place to look at anti-racism work and ended up suffering from the very thing I was trying to help with."
Speaking to the BBC, he said "That was something I found really difficult: being silenced constantly, feeling unheard, critiqued, scrutinised, gaslit, just not feeling believed."
He described black firefighters writing to senior management detailing their experiences of racism who were never subsequently contacted.
Fire commissioner Andy Roe told BBC London this week that "as an organisation we've got to be judged on delivering that change and that change has started now". He said it included outsourcing the handling of complaints to external experts.
He described some of his staff's behaviour as "inexcusable" and something that "destroys all we stand for" but said he had a "relentless energy" to address the problems facing the brigade.
The independent review into the brigade's culture listed multiple examples of racism, misogyny and poor behaviour at almost all levels of the organisation. LFB has accepted the report, and its 23 recommendations, in full.
Mr Dawes advises against any women or black Londoners joining LFB. "No, not right now. All you're doing is bringing more and more people into harm. If you're not tackling the toxic culture at the same time as bringing people in, then you're just creating more issues.
"If you're coming in and you're from an oppressed group then you don't get to set the standards of what the behaviour is at the station, or at headquarters. You have to fit in. You've got no choice. Either that or your life's hell. And as soon as you raise your head above the parapet, it's over."
Mr Dawes eventually left LFB in September, after a 21-year career.
He said he had repeatedly stressed his desire for better education within LFB.
"If the brigade push robust education around what good behaviour looks like around the station, what discrimination actually looks like, then you can have a zero-tolerance approach because you've taught these people and allowed them to understand it.
"You're not just telling them what to do, you're bringing them along on the journey towards an anti-racism agenda. But none of that work's been done.
"So far the brigade have never ever taken responsibility to actually educate people. I just find that so weird."
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