The Church of England's parliamentary body has apologised to victims of sexual abuse at the hands of Anglican clergy, noting its failure to prevent it and respond effectively.
The Archbishop of Canterbury, the Most Reverend Justin Welby, said addressing the issue had been "absolutely agonising".
Speaking in a meeting of the General Synod in York on Sunday, the Archbishop admitted some victims had been "badly treated" by the Church.
He said there needed to be a "complete change of culture and behaviour" in the Church of England.
"We cannot in 20 years be finding ourselves having this same debate and saying 'Well we didn't quite understand then'," he said.
"There has to be a complete change of culture and behaviour and in addition there is a profound theological point. We are not doing all this, we are not seeking to say how devastatingly, appallingly, atrociously sorry we are for the great failures there have been for our own sakes, for our own flourishing, for the protection of the Church.
"We are doing it because we are called to live in the justice of God and we will each answer to Him in our failings in this. Accountability is one we must take with the utmost seriousness."
The Archbishop stressed however that the Church of England was still only at the beginning of a lengthy and costly process to change the culture within the Church.
"Culture change is by far the hardest one to do. Many parts of our society are trying to deal with culture change in the way that large organisations, groups of people, clubs, whatever it is, behave, and it is very trying to find a way of facing those issues," Archbishop Welby continued.
"And therefore we require enormous determination to do so, so that we have a culture that looks first to justice, to transparency, to clarity, to admission of where we have failed.
"This change must be done with the survivors, not to them. We have spent very many years doing things to them. We must only act with them and that will mean much more than we imagine as we listen and reflect on dark and desperate acts in the past."
The General Synod voted overwhelmingly in favour of an apology offered "unreservedly" by the Archbishops of Canterbury and York "for the failure of the Church of England's systems to protect children, young people and adults from physical and sexual abuse inflicted by its clergy and others and for the failure to listen properly to those so abused".
There were 360 votes in favour, none against and no recorded abstentions.
The Bishop of Southwell and Nottingham and chair of the Church of England's safeguarding group, the Right Reverend Paul Butler, told General Synod earlier in the debate that the Church of England's failings in child protection were "sin just as much as the perpetrators sinned".
The debate in York follows investigations into abuse in the Diocese of Chichester which resulted in a visitation and report criticising the "dysfunctionality" within the senior diocesan team. Following the visitation, fresh allegations of abuse arose in relation to the Dean of Manchester, the late Robert Waddington, which are now subject to a new independent inquiry.
Bishop Butler said the investigation into abuse in the Diocese of Chichester had exposed much wider institutional failings affecting every diocese in the Church of England.
"For far too long the institution, and notably those in most senior positions, either disbelieved the stories that survivors told us or believed them but tried to hide the truth away or remove the offender elsewhere vaguely hoping that 'the problem' would go away," he said.
"We can make all the excuses that we like about society being different in previous decades, or our understanding of abuse being so much better. We can note that our policies were different then and we followed those policies.
"But these take nothing away from the fact that we failed to listen properly, we did not acknowledge the wrong done, and we protected the institution at the expense of the person abused.
"We cannot do anything other than own up to our failures. We were wrong. Our failures were sin just as much as the perpetrators sinned. By failing to listen or act appropriately we condemned survivors to live with the harm when we should have been assisting them into whatever measure of healing might be possible."
There was broad support within Synod to drop the 12-month time limit for complaints about abuse to be brought forward.
There were also calls for a uniform child protection policy to ensure consistency across the Church of England.
That call had the support of the Bishop of Chichester, the Right Reverend Dr Martin Warner, who also spoke of his hope to see a shift in culture towards a "humbler church, a more compassionate church, a more humane church, a church which understands how to listen".
However, Synod was warned that even good policies properly implemented would never stamp out abuse completely.
Caroline Spencer, Synod member from Canterbury, said churches were "honey pots" for abusers and that the church's open door policy made it difficult to check everybody who came into the church.
The Reverend Jonathan Alderton-Ford, from Bury St Edmunds, echoed these sentiments, saying churches were being targeted and "infested" by organised abuse gangs.
There were also warnings of the "mass grooming" of parents and congregations.
The Bishop of Hereford, the Right Reverend Anthony Priddis, called for "informed vigilance" to complement good policy.
Perfect policies perfectly implemented would not stop abuse sadly. They are necessary for us to have, the best policies we can, it is necessary to have them of course implemented in the best way. There is no space for any of us for complacency. There never has been there never will be.
"We need each of us to be informed, we need each of us to be vigilant, and I regret to say at times we need to be suspicious because people who have a tendency to abuse are very often not only devious and clever and we know that grooming refers not just to grooming children but to grooming us, grooming adults, grooming institutions.
"We know it is true within the church and tragically it has been revealed very clearly within the BBC and other institutions. Informed vigilance must go with our best policies."