Authorities have vowed to crack down on judicial corruption concerning sentences and probation following a number of cases of convicts bribing their way out of jail.

"Terms and procedures on commutation, parole and serving a sentence outside jail for medical reasons should be stringent within the framework of the law," said an instructive document released on Monday by the Party's Commission for Political and Legal Affairs.

In one high-profile case, Zhang Hai, former board chairman of Jianlibao Group, a Chinese beverage giant, used illegal means to have his sentence cut by five years in a second court trial and had his jail term further reduced by more than four years while he was serving the sentence.