The Small Charities Coalition has denied that its trustees told its former chief executive that she could not continue speaking out about diversity if she wanted to remain in the role.
Mandy Johnson stepped down from the umbrella body in September after just over a year in the position.
In the summer, Johnson took part in a Third Sector article and photoshoot celebrating the number of women leading charity sector representative bodies.
But she subsequently issued a statement on Twitter on behalf of the SCC expressing her regret about taking part in the article after some in the sector criticised it for its lack of diversity.
Third Sector understands that Johnson's actions exacerbated tensions between her and SCC's board, and subsequently led to her leaving the charity.
In the first episode of a podcast called This is Not the Mandy Johnson Show, Johnson talks about her departure from the charity.
She says that during her time at the SCC she had become more interested in diversity and had begun speaking out more about the subject.
"Because I was getting louder and louder about diversity, I think a bit of friction started to rise between me and my board," she says.
"I guess, to cut a long story short, the louder I was getting about diversity the more uncomfortable I was making my board."
She adds: "…there was a moment when I made a very loud noise about something that I perceived to be racist, and my board didn’t agree."
She later says in the podcast: "I was told quite clearly that if I wanted to carry on in that job then I couldn’t speak in public about diversity any more, and for me it’s just too much of an important issue for me to remain silent on."
Johnson also talks in the podcast about her struggles with mental health issues.
A statement from the SCC said it was aware of allegations made by Johnson in the podcast.
"However, claims made that the board required Mandy to choose between her job and her principles are not true," it said.
"As a member of the infrastructure bodies group on equality and diversity, SCC is committed to the agenda championed by ourselves and colleagues across the sector."
The statement said the SCC was committed to championing equality and diversity and had been since its inception.
"In addition, we expect our staff, volunteers and trustees to behave with integrity and with due respect towards each other and everyone we work with."