The chief executive of the Jockey Club has resigned after an independent inquiry upheld allegations of bullying, racist comments and the circulation of offensive material.
Delia Bushell, who had been in the role since September 2019, tendered her resignation on Sunday, having been informed that disciplinary action had begun "on the grounds of gross misconduct".
It is understood the barrister who led the investigation also found evidence of witness tampering by Bushell.
The Jockey Club's board concluded it was "untenable" for her to remain in the position.
The Jockey Club - which operates 15 racecourses including Aintree, Cheltenham, Newmarket and Epsom Downs - announced it has appointed Nevin Truesdale as acting group chief executive following Bushell's sudden departure.
In a letter published in the Racing Post, Bushell expressed her "shock and sadness" at the decision.
She added: "I have been subjected to unmerited, dishonourable, bullying behaviour by people I previously held in high regard and trusted.
"Given the toxicity of the working environment I find myself in, the predetermination of the disciplinary and the clear and ongoing threats to my reputation, I have no choice but to accept the repudiatory conduct described in this letter and to resign with immediate effect."
The England and Wales Cricket Board - where Bushell is a director - said in a statement: "We do not underestimate the seriousness of the claims made against Delia, but we will seek to review and discuss what is clearly a complex matter with both her and the Jockey Club before commenting further."
Bushell is also on the board of Commonwealth Games England.
A spokesperson for Commonwealth Games England said: "We are aware of reports in the media concerning Delia Bushell and will not make any further comment until we have reviewed the situation."