'Prisoners have to work days and nights - not just men but children below 16,' he said.

Their diet consisted mainly of coarse rice, he said. Oil and meat were not available. 'Occasionally, we would have some vegetables but they tasted like toilet paper because the cooks had no oil to cook them in,' he said.

The former prisoner said his labour camp housed more than 1,000 prisoners. Most were thieves, hooligans and prostitutes. Few were political prisoners.

He said although they had to work almost incessantly every day, they were rarely paid.

'Everybody had to work. I saw a handicapped boy who had only one arm and one leg who had to work in the fields every day with his mother. They locked the boy in the camp because his mother was a prisoner.' The former prisoner said he was sent to a clinic after his family paid more than 10,000 yuan (HK$9,330) to bribe camp officials. 'I knew this guy who came from my home village and he sympathised with me. So he helped arrange for me to fake sickness and I was allowed to stay out of work,' he said.

He said the clinic was not a proper clinic because it offered no medical services. But prisoners sent there were spared hard labour.

Other prisoners who were rich and could bribe officials were assigned to take charge of clerical work such as propaganda work and accounting.

Another ex-prisoner, who served three years in a labour camp in Jiangsu, said although regulations said prisoners should spend time in re-education sessions, he had not done so.

'These camps are strictly profit-making. The officials used the prisoners as slaves to enrich themselves,' he said.

Inmates who refused would be physically punished or their prison terms would be extended.