Lawyer Barry Hart wants an inquiry into Auckland Prison after the death of a second inmate there in less than a month.
Another male inmate died on Sunday morning in the prison at Paremoremo.
Convicted killer Antonie Dixon was found dead in his cell there on 4 February. Dixon was awaiting sentence for murder and maiming two women with a samurai sword in 2003.
Few details about the latest death are available. The Corrections Department won't make any comment until next of kin have been notified.
Dixon's lawyer Barry Hart says the latest death raises serious questions about whether inmates receive adequate care.
Corrections Association president Beven Hanlon says the situation at Auckland Prison is a disgrace and security and safety are not taken seriously by management.
He says Paremoremo has become New Zealand's most dangerous prison.