The group justified their decision on Monday, stating they do not intend to be part of a committee to be elected there to take the PD to a congress.

The ruling PD continued to teeter on the brink of a major split that could have repercussions for the future of Premier Paolo Gentiloni's government.

On Sunday ex-premier Matteo Renzi quit as head of the PD at a party assembly in order to trigger the process for a new congress, through which he is expected to seek a fresh mandate.

Mr Renzi said that he would not let the threat of a split from members of a significant left-wing minority within the group "blackmail" him into backing down and not standing for leadership again.

Tuscan Governor Enrico Rossi said on Monday that he was considering terminating his membership of the PD.

"I was just thinking of sending back my membership card to my section, with a letter," Mr Rossi told Rainews 24.

Mr Rossi, Puglia Governor Michele Emiliano and former PD House whip Roberto Speranza accused Mr Renzi of creating the split by not taking account of the minority's demands.

On Sunday Mr Emiliano spoke at a PD assembly and suggested there was still a possibility that the split could be averted.

Mr Renzi resigned as premier in December after almost three years in office following the rejection of his flagship constitutional reform in a referendum.

Several prominent members of the minority campaigned for a “No” vote in the referendum.

Mr Renzi's place was taken by former foreign minister Mr Gentiloni, also a PD member.

Mr Rossi said on Monday that an eventual splinter should continue support Mr Gentiloni's government.

"This question should be put to those who sit in parliament, but I think it is normal that it [a new group] would support the government," he told Rainews24.

Former premier Enrico Letta made an appeal on Monday for PD members to avert a split.

"I look at the break-up of the PD with astonishment," Mr Letta, who was ousted as premier by Renzi in 2014, wrote on his Facebook page.

"I say to myself that it cannot finish like this. It must not finish like this. Today I don't have anything but my voice and I cannot do anything but use it to call for generosity and reasonableness."

Justice Minister Andrea Orlando and two other senior PD members, Gianni Cuperlo and Cesare Damiano, decided at a meeting late on Sunday to set up a new “area” within the party.

The three, who called for unity at a party assembly on Sunday, agreed on the need for a new area to propose new policies to revamp the PD.

With ANSA