The group chief executive of the Jockey Club is standing down after a review found evidence to support allegations of bullying towards colleagues and inappropriate racist comments.
Delia Bushell was one of 19 witnesses interviewed as part of a review into allegations about her conduct and the findings made it "untenable" for her to stay in the role, the organisation's board said.
The former TV executive was given the job little more than a year ago and described as a "first-class appointment" at the time.
She had said she was "excited and honoured" about the role and was "looking forward to working with the talented team" at the club.
The Jockey Club, which owns a number of high-profile tracks including Aintree, Cheltenham, Epsom and Newmarket, said an independent barrister had submitted a detailed report to a sub-committee of the board last week.
That sub-committee, which includes Tory peer Dido Harding - who is in charge of the NHS Test and Trace system - decided there was a basis for disciplinary action against Ms Bushell including on the grounds of gross misconduct.
In a statement, the Jockey Club said: "The board of The Jockey Club announces today that Delia Bushell is to stand down as group chief executive with immediate effect.
"This follows the completion of an independent review into a wide range of allegations about her conduct, which the board concluded made it untenable for her to continue in the role.
"As part of this review, an independent barrister interviewed 19 witnesses including Delia. He submitted a detailed report to a sub-committee of the board comprising Dido Harding, Julia Budd and Justin Dowley on Sunday 23rd August in
which he concluded that there was evidence to support a number of the allegations of misconduct including bullying behaviour towards colleagues, inappropriate racist comments and sharing offensive materials.
"The sub-committee of the board agreed with his conclusion and decided that there was a basis for disciplinary action against Delia including on the grounds of gross misconduct. This recommendation was accepted by the full board of The
Nevin Truesdale has been appointed as acting group chief executive, the Jockey Club said.