A Cardiff City internal investigation into claims of bullying has found “a number of significant concerns”.
The club said its investigation has looked into accusations of bullying and abuse by current and former employees.
Cardiff has not named any individuals involved as the report “forms part of an employee disciplinary process”.
Last January, Craig Bellamy stepped down as Cardiff Under-18s coach after the club’s decision to investigate a bullying claim against him.
It followed reports of a complaint about the former Wales striker’s alleged treatment of a young player, who has since left the club.
Bellamy, 40, who played for clubs including Cardiff, Liverpool and Manchester City, denied those allegations.
Cardiff says its investigation has found there was an unacceptable coaching environment and a lack of safeguarding processes.
The Championship club has apologised for any distress caused and pledged to implement changes to protect young players in future.
The club has shared the investigation’s findings with concerned parties including its board of directors, the Premier League, the Football Association and the Football Association of Wales.
A Cardiff statement read: “The investigation… highlighted a number of significant concerns relating to an unacceptable coaching environment over the relevant period of time.
“This was magnified due to the lack of effective safeguarding processes being followed. Cardiff City Football Club regrets the impact this has had and any distress that may have been caused to those affected by the investigation process that has followed.
“We can provide reassurance that robust changes to procedures have subsequently been implemented and awareness of these issues will be reinforced for the protection of young players at Cardiff City Football Club.
“This… has allowed the club to address previous failings and implement processes and procedures in the most thorough way to prevent similar issues arising in the future.”