The former head of the Welsh public service broadcaster has sent a scathing letter to the culture secretary calling on her to urgently investigate S4C and its chair, amid a deepening crisis at the top of the Welsh-language channel. Siân Doyle, who was sacked as chief executive of the taxpayer-funded S4C on Friday, sent the letter to Lucy Frazer calling on her to examine the actions of the channel’s chair, Rhodri Williams, before he is appointed for a further term in the role. Doyle states that she had “repeatedly” alerted the Department for Culture, Media & Sport to concerns, but had been told internal issues were for S4C to address. She wrote: “[H]ad the issues taking place in S4C taken place in England – in the BBC or Channel 4 – would DCMS have taken the same hands-off approach?” It comes after Doyle was sacked following complaints in April by the Bectu union of “a culture of fear” within the organisation. S4C, which receives £89m in licence fee funding every year, said it decided to sack Doyle after receiving legal advice following an independent investigation. Doyle said the manner of her dismissal demonstrated an “unprecedented lack of governance for a public body”. The S4C board said: “The nature and weight of the evidence provided was deeply troubling” and after receiving legal advice it had taken “the difficult but unanimous decision to terminate the employment of the chief executive”. It added: “We recognise that we need to restore confidence and trust in the organisation – not only amongst our staff but with our partners in the creative sector, audiences in Wales and beyond.” Doyle denied accusations of bullying, and told the Guardian she planned to sue the broadcaster for unfair dismissal. She said she had been dismissed by letter, without seeing the report and without a right to appeal in what she told Frazer was a “cavalier approach to employment law” which left “S4C open to significant legal risk”. In her first interview since her dismissal, Doyle said she believed sexism had played a role in her treatment, and that she had been “hung out to dry” by the organisation. “I think sexism did play a role in the fact that I’m a strong lady who is an experienced leader, who wasn’t doing what [the chair] wanted,” she said. In the letter Doyle accuses Williams of embodying a culture of “fear, lack of trust and excessive control” at the broadcaster, claiming that the current board had little influence over a chair who terrified some individuals in the organisation. Doyle wrote it was her “firm view” that the “lack of governance and oversight of the organisation causes a significant legal, financial, ethical, organisational, and political risk”. Doyle – who grew up in a politically active Welsh-speaking household – said she had been given a mandate to change S4C when she became chief executive two years ago, which was embraced by some staff members and opposed by others. She said during her tenure,audience numbers had increased, with more young viewers, and there had been a flagship deal with the Canadian-American actor and film producer Ryan Reynolds to screen Welsh-language programming on his digital channel. In April this year a letter written by the Bectu union said staff were undermined and disrespected by senior executives and “often left in tears”. It said management was “aggressive and confrontational” when concerns were raised. At the time, union officials said Doyle had acknowledged staff concerns, but had also suggested that the term “bullying” was used too often. Doyle said she was aware of criticisms of herself but some came from “very vocal former employees”, adding: “But that’s part of a transformation. It’s a culture change.” Doyle said she had not seen the independent report carried out by the firm Capital Law, which heard from 96 people and resulted in her sacking, but said she understood that it also heard allegations of bullying against the chair. Asked for a response to the allegations made by Doyle, Williams and S4C said they had “nothing to add” to Friday’s statement. The statement said the broadcaster would publish a further report on the evidence. Doyle, who was the managing director of the telecommunications company TalkTalk before coming out of retirement to take the post of S4C’s chief executive and accounting officer in January 2022, said she had never faced accusations of bullying at previous companies. “The last nine months are probably the most extraordinary and horrific I’ve ever had in any business, and I’ve worked in really challenging, male-driven businesses,” she said. “I want to say on the record, I’ve managed probably about 30,000 people in my time [before S4C] and I have not had one grievance, not one bullying allegation against me, no complaint ever. I am completely unblemished.” The sacking comes weeks after a bullying row at the organisation spilled into the public domain when S4C’s chief content officer, Llinos Griffin-Williams, was sacked by Williams, after it was alleged she made abusive comments to Mike Phillips, a rugby pundit and former player. She denied gross misconduct and comments attributed to her and said she had been dismissed without a fair investigation. Several weeks before her dismissal the S4C board upheld a bullying complaint made by Griffin-Williams in which she said Williams had behaved in a “threatening, aggressive, intimidating and bullying” way towards her during a meeting in June. Doyle said she was not consulted about the decision to fire her right-hand woman and she took sick leave as a result of the stress. “It wouldn’t happen at the BBC or at Channel 4 and it shouldn’t happen in Wales,” she said. “This channel is so important, it’s funded with taxpayers money and the audience in Wales deserves better.” Doyle said the DCMS had been “incredibly supportive” of S4C but when she had raised complaints it said they had to be dealt with by the channel. “But I keep coming back to the phrase: who guards the guardsmen?” she said. Doyle said her experience at S4C had been “punishing”, and that she felt the broadcaster had not demonstrated a duty of care towards her. “This has taken a huge toll, and my family have gone through hell,” she said. She said she hoped the strategy she had driven would continue. “We were starting to see the green shoots of recovery,” she said. “I just hope that somebody can take the role [of chief executive] and is given the mandate to transform it, rather than being stopped at every stage along the way.”