Andrew Graystone has defended his new book on the John Smyth abuse scandal against critics who say it is inaccurate.

In Bleeding for Jesus: John Smyth and the cult of Iwerne camps, released on Thursday, Graystone details horrific accounts from survivors, and questions why the abuse was allowed to continue after it first came to light in the early 1980s.

Many of the victims attended the Iwerne evangelical camps but Smyth was never held to account and instead relocated to southern Africa where the abuse continued, and where he was charged but never prosecuted over the death of a 16-year-old at his Zimbabwe camp.

Smyth died in 2018 after a Channel 4 News exposé. It was Graystone who approached Channel 4 News presenter Cathy Newman to investigate the abuse.

In his book, Graystone writes that for some, "the call to live out the gospel in the form in which it is represented by the Iwerne movement is of such overwhelming importance that they feel that furthering that work is more important than telling the truth about it."

He continues, "Over the past six years I have researched the life and influences of John Smyth. I wanted to explore how a Christian leader could conduct such an extensive campaign of physical and spiritual abuse whilst hiding in plain sight.

"I wanted to understand how other Christian leaders who knew what he was doing could choose to turn a blind eye. And I wanted to assess the extent to which the culture and theology of evangelicalism had shaped and enabled his abuse."

In a statement last month, the Titus Trust - formerly Iwerne Trust - admitted it should have gone to the authorities when the allegations first came to light in 1982.

"We recognise that at times we have failed to show our concern for the victims and survivors of John Smyth's abuse," it said.

"The welfare of every victim and survivor should always have been our main priority. We can see that we could have done more, perhaps alongside independent experts, to reach out to victims and survivors and work with them in shaping our responses.

"In seeking properly to discharge our regulatory duties and in establishing that we did not have legal responsibility for Smyth's abuse, we have not always displayed all the Christian love and compassion that should be expected of an organisation committed to making the Christian gospel known.

"We are deeply sorry for the additional pain that we caused for a number of these men and their families."

The trust also said it was awaiting the outcome of the Church of England's independent review being led by Keith Makin, which is still in the evidence-collecting stage and is due for publication in 2022.

The trust added, "We believe that it is vital for the truth to be made known in a case like this. This is especially important for those who have suffered so much harm."

There has been some strong criticism directed towards Graystone over his book.

Titus Trust's former Operations Director James Stileman has claimed there are "inaccuracies" and "misleading" information concerning himself.

In a lengthy statement, he denied being involved in a cover-up and said Graystone had done a "disservice" to victims by publishing his book before the completion of the Makin Review.

"Undoubtedly major errors of judgement were made, and hard lessons will need to be learned from this terrible saga. But as someone who features prominently in Graystone's account, I am astonished how inaccurate some of it is," he said.

"If material that relates to me is inaccurate, misleading or untrue, what else in the book is wrong? This is not helpful for those who want to know the truth about what happened, particularly survivors who have suffered greatly from the lack of reliable information to date."

He added, "I have no doubt that I got some things wrong in the course of my involvement with the Smyth matter, and I am prepared to accept and apologise for any failings that Makin identifies. But I reject any suggestion that I was involved in a cover-up, which Bleeding for Jesus implies on a number of occasions."

Evangelical publisher Julia Cameron said the book contained "many factual errors" and that some of the blame apportioned to former Iwerne camps leader David Fletcher in failing to go to the police in 1982 was "unfounded".

"[Graystone] imaginatively reconstructs scenes, and quotes from them, while not having spoken with those present," she said in a review for Evangelicals Now.

"[T]he narratives relating to the Titus Trust (successor to the Iwerne Trust) and relating to David Fletcher, leader of the Iwerne camps, hold errors and wrong assumptions, some scurrilous.

"This lack of careful recording should encourage readers to handle the whole text with caution."

In the last few days, Graystone has also been accused of unfairly 'outing' a Smyth survivor against his wishes.

Alasdair Paine, vicar of St Andrew the Great, Cambridge, said in a statement, "Mr Graystone has never contacted me to ask for permission to identify me as a survivor or to tell my story - indeed, he has never asked for my own account."

In a separate statement, church wardens Piyush Jani, Matt Byatt and Ugo Akuwudike said they were "appalled at how any author or publisher could think it right to 'out' a victim without their consent and in this way."

Responding to the claims, Graystone denied outing any survivors against their will, and stood by the content of his book.

"I am sad but not surprised that this book challenges people for whom the Iwerne network has been a precious source of identity," he said.

"I hope they will find enough perspective to reflect deeply on what has happened, and learn from it."