Justin Welby, the former archbishop of Canterbury, has said his failure to take effective action over a serial sadistic abuser was because he was “overwhelmed” by the scale of the abuse crisis in the Church of England.

In his first interview since resigning last November, Welby said: “Every day more cases were coming across the desk that had been in the past, hadn’t been dealt with adequately, and this was just, it was another case. It was an absolutely overwhelming few weeks.”

This was not an excuse, but a reason for his failures, he told the BBC’s Laura Kuenssberg. “The reality is I got it wrong. As archbishop there are no excuses.”

He also said there was a “rush to judgment” of public leaders.

“There is an absence of forgiveness; we don’t treat our leaders as human. We expect them to be perfect. If you want perfect leaders, you won’t have any leaders.”

Welby became the first archbishop in more than 1,000 years to quit after an independent review found that he should have taken more robust action over allegations of abuse by John Smyth. His resignation, announced days after the review was published in November, plunged the C of E into crisis.

About 130 boys are believed to have been victims of Smyth, a powerful barrister who died in 2018. An independent review by Keith Makin into the abuse concluded Smyth could have been brought to justice had the archbishop formally reported it to police a decade ago.

Welby and other senior figures in the C of E were told of allegations that Smyth had abused dozens of boys who attended evangelical Christian holiday camps, beating them viciously in his garden shed.

Welby had volunteered at the holiday camps in the late 1970s but said he was unaware of the allegations at the time. The Makin review said Welby was informed of the abuse allegations in 2013 but failed to take action, and that it was “unlikely” he would have been unaware of rumours surrounding Smyth when he was volunteering at the camps.

The review said: “[Welby] may not have known of the extreme seriousness of the abuse but it is most probable that he would have had at least a level of knowledge that John Smyth was of some concern.”

In his resignation statement, Welby said: “It is very clear that I must take personal and institutional responsibility for the long and retraumatising period between 2013 and 2024.”

One of Smyth’s victims, known as Graham, who reported the abuse allegation in 2013, told the BBC: “The archbishop suggests he was just too busy. No one should be too busy to deal with a safeguarding disclosure. The archbishop has never answered why there were not enormous red flags when told about horrific abuse.”

Welby’s successor as archbishop of Canterbury is expected to be announced in the autumn after a lengthy and opaque selection process led by the UK’s former spy chief, Lord Evans of Weardale.