The archbishop of Canterbury elect, Sarah Mullally, has been accused of contravening the Clergy Discipline Measure code of practice during her time as bishop of London.
One member of clergy has now called for an independent investigation to be launched.
According to Premier Christian News, 'Survivor N' first reported allegations of abuse against a priest in the diocese of London over a decade ago.
Premier Christian News has now "seen evidence" that Mullaly "contravened the Clergy Discipline Measure [CDM] code of practice" by "sending a confidential email about the allegations directly to the priest concerned, outside of the CDM process".
According to the Church of England, CDM "provides a procedure for handling such allegations of serious misconduct".
Mullally allegedly told Survivor N his claims were "unsubstantiated". Survivor N says he was then subjected to a "systematic campaign of harassment and retribution".
The decision of the diocese and Mullally not to investigate Survivor N's claim left him "in such a severe mental health crisis that he attempted to take his own life twice".
A former child protection lawyer described the diocese's treatment of Survivor N as "the worst example of post-abuse victimisation of a CDM complainant we have ever seen".
Survivor N filed a formal complaint against Mullaly for her handling of the case. In 2020, the complaint was acknowledged by the then bishop at Lambeth, Tim Thornton.
Yet when Thornton was contacted 16 months later by Survivor N's lawyers, he claimed the complaint had "only just been received by Lambeth Palace".
A psychiatrist said Survivor N's mental health "deteriorated sharply" during this time. Survivor N says he is still awaiting a formal response.
Survivor N said: "All of this reminded me how little my life is worth, how meagre my human value, in the face of the cartel of Establishment … The injustice and dehumanising collusion felt overwhelming to the point that life wasn't worth living."
'Toxic' culture at diocese of London
A former employee of the diocese, 'Victoria', also attempted suicide after raising concerns about "the mishandling of safeguarding allegations by the Church's senior leadership". She described the culture as "toxic" and said she was left "isolated and excluded".
Victoria, who had a long career in safeguarding, worked with the diocese until 2025, and described a "wall of silence when there's concerns raised".
She said: "I was framed as a troublemaker, framed as a hysterical woman, and it made me very ill … Everything was being turned on someone who raised their voice. A very disappointing response from female senior leaders as well."
A former diocese of London vicar told Premier Christian News he developed PTSD because of how he was treated after he raised safeguarding concerns.
The diocese's communications team has refused to comment on the allegations.
In October, advocate for victims of Church abuse Andrew Graystone said Mullally's appointment as archbishop "has caused real shock and dismay amongst victims and survivors who have been in touch with me. The Diocese of London has a disastrous track record of safeguarding failures."
"We had hoped that a new archbishop would be able to move the Church forward in its safeguarding practices. This appointment doesn't do that. If anything, we are starting further back. Sarah Mullally has yet to demonstrate that she really understands abuse, and that she prioritises the care of victims over the Church's reputation", he added.
'Insufficient urgency' at CofE to address safeguarding failures
Last month, the Charity Commission told a Church of England body it "must rapidly accelerate the delivery of safeguarding improvements and close gaps in its approach to handling complaints".
The commission told the Archbishops' Council there is "insufficient urgency and pace in implementing responses to past safeguarding reviews, and the current approach to doing so is fragmented and overly complex."
The commission started engaging with the Archbishops' Council following the publication of the Makin Review last year, which found that the erstwhile archbishop of Canterbury, Justin Welby, "could and should" have reported sadistic abuser Jon Smyth to the police in 2013.
Welby was subsequently forced to resign.
NSS: 'Mullally mired in abuse scandals before she is even installed'
National Secular Society spokesperson Alejandro Sanchez said: "These allegations raise grave concerns about Sarah Mullally's safeguarding record. They should now be thoroughly investigated.
"It speaks volumes about the CofE's institutional culture that Justin Welby was forced to resign in disgrace over safeguarding failures, and that Sarah Mullaly is already mired in abuse scandals before she has even been installed.
"Privileging one denomination of one faith with established status is wrong in principle, but it is even more reprehensible given the Church's diabolical record on abuse."