Ten former employees at a homeless charity have said the chief executive's behaviour led them to leave their jobs.
Since 2011, seven managers and three members of staff have left Gisda, with many claiming to have been bullied.
The board of directors at the charity, based in Caernarfon, Gwynedd, said it had confidence in the ability of Sian Elen Tomos.
The youth charity is "committed to creating a healthy work space for its entire staff," the board added.
The BBC has spoken to 10 former Gisda employees who claim Ms Tomos's managerial style was the reason they left.
None were willing to do an interview publicly - but one agreed to speak anonymously.
Eileen - not her real name - said Ms Tomos "could make people feel very uncomfortable".
"Not taking into account what anyone else said, ignoring people and making it obvious in front of other people, turning her back on you as you were speaking to her and walking away," she explained.
"I've seen her walking out of a number of meetings. She would not speak to people for days. Not speaking at all. And she could be nasty to people too.
"I think she worked on people's weaknesses - bullying, really."
She said she felt "sick" and "felt for her friends".
"I didn't want to go to work," she added. "I think it affected young people too. They could see so much turnover.
"There was a feeling that she was untouchable. If anyone disagreed with her she got rid of them - or worked to get rid of them."
A letter sent to the board of directors and seen by the BBC shows a number of staff complained about the situation in 2017.
The BBC understands only three formal complaints have been made since 2011, but a number of former staff said they did not complain formally because they felt they would be ignored.
The letter noted staff felt "suspicious, dispirited, anxious and angry", and the charity needed to act decisively if the board wished "to avoid a morale crisis".
The letter finished by calling on the board to "consider the high level of staff turnover in the organisation".
Later in 2017, an independent report was commissioned by the charity in response to the grievances of two managers.
The BBC has seen a copy of the report, which states the grievances of the two previous managers and the complaints made by the chief executive about her staff, were partly upheld.
Acknowledging further issues at Gisda, the report made a number of recommendations.
These included to arrange mediation between Ms Tomos and the two former managers and the board should review its complaints procedures so complaints were acted upon and not ignored.
According to Eileen, who left months after the independent report was published, the recommendations were not acted upon.
Four other former members of staff who left after the report was published agreed.
To see positive change, Eileen said the charity should appoint a new board of directors and chief executive.
Ms Tomos and the chairman of the board of directors, Tudor Owen, were given the opportunity to respond separately to the claims.
In a response on behalf of the pair, the board of trustees said it took "any suggestion of bullying or wrongdoing seriously as it was against the inclusive ethos that was created".
The statement added the board had "complied with their legal obligations" and the matters raised "had been given appropriate internal attention".
In conclusion, the board said it had full confidence in Ms Tomos.
A Gwynedd Council statement said Gisda received funding from the authority to provide services to support young homeless people and, as part of the contract, it was regularly "monitored and scrutinised".
"We will be asking Gisda that none of the matters that have been raised recently affect their contract with the council in any way," it said.