Rome, February 15 - Democratic Party (PD) leader Matteo Renzi said Wednesday that he wants his opponents within the centre-left group to attend a party congress and challenge his ideas, rather than breaking away. "The verb for the congress and the primaries is not 'go away!' but 'come', bring ideas, bring dreams, bring criticism," the ex-premier said in his E-news newsletter. A left-wing minority within the party that is critical of Renzi is threatening a split. On Tuesday former PD leader Pier Luigi Bersani said the split has effectively already happened.