Cancellieri is embroiled in allegations that she used her influence to help ensure Giulia Ligresti, who reportedly suffers from anorexia and anxiety, was moved from prison to house arrest.
Ligresti is the daughter of Salvatore Ligresti, an insurance tycoon who is also in prison for alleged involvement in false accounting at Fonsai insurance group, of which he was honorary chairman.
Cancellieri has rebutted the claims, insisting earlier this month that she had not acted beyond her remit. She said the decision to move Ligresti was made by a court, based on an independent medical examination.
Though she has won the backing of Prime Minister Enrico Letta, there have been increasing calls from within his centre-left Democratic Party (PD) for her to be dismissed after new reports of phone conversations with the Ligresti family emerged in the daily newspaper, La Repubblica, on Friday.
Cancellieri had earlier admitted asking prison authorities to evaluate Ligresti's health and published transcripts of her phone calls appeared to show her promising the woman's family she would deal with the matter.
She told the Senate she had "acted in the same way as in this case in many other cases... over 100 in the past few months alone", in the face of "an unacceptably high suicide rate in prison".
"Every death in prison is a defeat for the state and the prison system. I feel the weight of the situation and have dedicated a not insignificant part of my time to the prison problem," she said.
The justice minister's critics accuse her of fuelling cronyism and of acting out of a conflict of interest because of her long friendship with the family.
Cancellieri's son, Piergiorgio Peluso, earned several million euros working as an executive at Fondiaria-SAI between 2011 and 2012.
"My personal relationships have never influenced my government work," Cancellieri said