South Africa announced last week that it would leave the ICC, following a similar announcement by Burundi.
Some African leaders have criticized the international body for interfering with their internal affairs.
In the case of South Africa, the government had rejected protests from the ICC after ignoring a court order for the arrest of Sudan’s President Omar Hassan al-Bashir, who is accused of crimes against humanity.
“We have noted with sadness the decision by the South African government to withdraw from the ICC,” the justice-and-peace commission of the bishops’ conference said in a public statement.
The group said that South Africa’s withdrawal might encourage other African nations to follow suit, harming the effectiveness of the international body.
The bishops’ conference suggested that South Africa should retain its membership in the ICC at least “until such a time that Africa has developed a credible and effective regional court.”