"We all have something in the past that we never want brought to light," Shin wrote on his Facebook page. "I, too, forever wanted to conceal and hide part of my past. We tell ourselves that it's okay to not reveal every little detail, and that it might not matter if certain parts aren't clarified."
Shin is travelling outside South Korea and has not answered requests for comment, although he is in touch with his wife and supporters, who say he is "very emotional" about the situation.
"Nevertheless this particular past of mine that I so badly wanted to cover up can no longer be hidden, nor do I want it to be," he wrote, apologising for the inaccuracies in his telling of his story.
Saying that his credibility might be too damaged for him to continue his work, he urged his supporters to continue their fight against the North Korean regime.
"Instead of me, you all can still fight. The world still needs to know of the horrendous and unspeakable horrors that are taking place."
Shin was forced to acknowledge the problems with his story after other defectors in South Korea began questioning his version of events and threatened to expose him.
In Escape from Camp 14 and in his testimony to the UN commission, Shin has said he was born and spent his life in Camp 14, a sprawling high-security political prison in the mountains north of Pyongyang, until his escape in 2005.
But Shin admitted to Harden at the weekend that when he was about 6, he, his mother and his brother were transferred to another prison camp, Camp 18, across the Taedong River from Camp 14.
In Camp 18, he learned that his mother and brother were plotting to escape and betrayed them to the guards, directly leading to their executions at that prison, not in Camp 14 as he had previously stated.
Shin also now says that he escaped from the camps on two occasions, in 1999 and 2001. Much of the worst torture he describes in the book as happening when he was 13, when guards suspected him of plotting to escape, actually happened when he was 20 and repatriated after escaping to China.
Human rights groups say the UN inquiry was based on interviews with scores of North Korean defectors.
"Its findings are still valid," said Brad Adams, Asia director for Human Rights Watch.
North Korea has already tried to undermine Shin's testimony and is certain to seize on these admissions to try to discredit him.
Human rights activists said that this could significantly set back the international campaign to indict Kim and his cronies for crimes against humanity.
Shin has been the most high-profile of defectors agitating for change in North Korea. In September, he was honoured by Human Rights Watch for his "tireless efforts to expose and end atrocities in North Korea", and more recently, he was featured in Light Through the Darkness, a report from the Bush Institute, part of the George W. Bush Presidential Centre.
Shin's tale: the revised version
*Shin's story originally drew widespread attention because he said he had been born and lived in a high-security political prison camp in North Korea from his birth until his escape through an electrified fence.
*He was said to be the only person who had escaped from such a camp.
*Shin now says he was transferred around the age of 6 to a lighter-security prison camp with his mother and brother.
*It was there, not the harsher camp, where he informed authorities about an escape attempt by his mother and brother. For that, they were executed.
*He now says he was later transferred back to the harsher camp.
*North Korea's Government denies the existence of the harsh political prison camps, and human rights groups and others rely on both information from defectors and satellite images for information.
*The UN commission of inquiry's report, released early last year, detailed abuses including mass starvation and forced abortions, and it recommended that North Korea's human rights situation be referred to the International Criminal Court.
- additional Bloomberg, AP
