Leftist veteran Manolis Glezos, a former SYRIZA MEP, called on the party leadership to "come to your senses" and hold a broad summit, saying that the country's third bailout "binds the Greek people hand and foot and enslaves them for entire decades."
"Let's not allow the Left to become a seven-month parenthesis," Glezos said in a statement.
Describing the government's strategy as "fickle and faltering," he accused the party's leadership of "erasing and destroying hopes and dreams."
"Finally come to your senses, fellow fighters and comrades of the leadership of the United Party," Glezos wrote.
"Before it is too late and before rushed initiatives are taken, listen to the voice of the people, of SYRIZA's organizations and call a broad summit," Glezos wrote, adding that "despite the intense dialogue that will take place, a solution will be found."