When Kim Tae Jin was being interrogated after his forcible repatriation to North Korea from China, he swallowed a nail in the vain hope of receiving medical treatment, rather than return to his prison cell.

When Kim Tae Jin was being interrogated after his forcible repatriation to North Korea from China, he swallowed a nail in the vain hope of receiving medical treatment, rather than return to his prison cell.

For the North Koreans, he had committed the ultimate crime: not only had he defected to China, but he was a Christian. The North Koreans found a bible in his bag, for which he suffered eight months of interrogation and four years in the Yodok political prison camp without trial.

In North Korea, there is only one religion - the official worship of the founder of the communist-ruled state, the late Kim Il Sung and his doctrine of self-reliance. Anyone who fails to show the necessary respect to the "Great Leader" and his son, Kim Jong-Il, the "Dear Leader", who currently rules the hermetically sealed communist state, risks being bundled off to labour camp.

Satellite pictures have shown the network of prison camps used by the North Korean authorities, but fewhave escaped with first-hand information about conditions inside. Yesterday, two North Korean defectors, Mr Kim and Kim Young Soon, a 67-year-old woman who lost three members of her family in the same camp, described the treatment meted out to Christians at Yodok.

Mr Kim said he was tortured after attempting to hold a meeting with other prisoners who had a religious background. The camp rules prohibited any gathering of more than two people. "Informers denounced us, and I was handcuffed and the guards stepped on my hands until they turned black," Mr Kim said. "They then took my clothes off. It was raining, and they made me sit on quick lime until my skin came off." Quicklime, or caustic lime, burns skin on contact.

After serving four years, Mr Kim was released as abruptly as he had been detained, and managed to escape in 2001 to South Korea. The Seoul-based NKGulag has issued a list of 616 people who are known to have disappeared into the North Korean gulag, where 100,000 people are held. Mr Kim said North Koreans were aware that such prison camps existed because of the sudden disappearance of entire families or neighbours without explanation.

"North Korea has got the worst human rights record of any country anywhere in the world," said Bill Rammell, the British Foreign minister.