The North Korean prison camp survivor who is the subject of the bestselling book Escape from Camp 14 has retracted some parts of his story.

Shin Dong-Hyuk, who testified before the UN Commission of Inquiry last year about his torture and forced labour in a prison camp that North Korea denies even exists, has changed the places and timing of some events in his story.

Blaine Harden, the author of the book on Shin's life, posted on his website that he learned the 32-year-old had "told friends an account of his life that differed substantially from the book" on Friday.

"Shin ... now says that he twice escaped to China from two different prison camps in North Korea. After his first crossing into China in 2001, he says he was caught after four months by local police and sent back to North Korea," Harden wrote.

It was upon his return that Shin says he was tortured for defecting to China. According to the Washington Post, he "was held in an underground prison for six months, where he was repeatedly burned and tortured" when he was 20, and not when he was 13 as was told in the book.

Shin's new story also places his mother's and brother's execution in a different camp. The Independent reports that a six-year-old Shin was transferred to the "less-severe-by-North-Korean-standards Camp 18" with his mother and brother.

It was in Camp 18, and not in Camp 14, that Shin told authorities about his mother's and brother's plan to escape and saw their executions.

Asked to "explain why he had misled" Harden, Shin said, "When I agreed to share my experience for the book, I found it was too painful to think about some of the things that happened.

"So I made a compromise in my mind. I altered some details that I thought wouldn't matter. I didn't want to tell exactly what happened in order not to relive these painful moments all over again."

Harden followed his post about Shin's admission with a corroborative evidence that supports the North Korean's claim that he defected to China twice.

The journalist cited a press release from the North Korean mission at the UN stating that in 2002, Shin "was arrested by Chinese border guards for illegal border crossing. Thereafter, he was transferred back to our law enforcement agencies ... [but] again made an illegal border crossing and ran over to the South."

According to the Independent, human rights experts said that while the essence of Shin's story remains the same, his admission of some inaccuracies to his account may make the case against North Korean leader Kim Jong-un weaker.

Following Harden's post about his retraction, Shin took to Facebook to air his apologies.

After saying that he no longer wishes to cover up part of his past that he previously "forever wanted to conceal and hide," he wrote that he is both grateful and sorry to the people who believed in him.

Shin added, "At this point I may or may not be able to continue in my work and efforts in trying to eliminate the political prison camps and bring justice to the oppressed ...

"But instead of me, you all can still fight ... For my family, for the suffering political prisoners, for the suffering North Korean people, each of you still have a voice ... On our behalf you must continue to spread what you know. The world still needs to know of the horrendous and unspeakable horrors that are taking place."