The SACP is purging members who have spoken out against the party "being at the forefront of the crusade" for ANC president Jacob Zuma to lead the country after next year's elections.
The group of six are from provinces that "did not support the move by the party to support Zuma for the ANC's presidency" because they doubted he would deliver to the working class.
They are former SACP spokesman Mazibuko Jara, Wits University sociologist Dinga Sikwebu, National Union of Metalworkers of SA official Tengo Tengala, hawkers union stalwart Pat Horn, former Gauteng secretary Vishwas Satgar and SACP Gauteng secretary Zico Tamela.
A confidential SACP "state of the organisation" report tabled at a recent central committee meeting says "senior members of the party in [Gauteng] have actively participated in attempts to establish a new rival left party. Can the party carry such members within its ranks?" asks the report.
"This matter [is] seen as a blatant disregard for party discipline and processes," it says.
SACP spokesman Malesela Maleka at first denied the existence of the report.
But he then said: "You should not have an internal report in the first place".
A source close to the group said SACP's Solly Mapaile had accused the group of wanting to link the envisaged party with the Congress of the People.
A member of the group, who spoke on condition of anonymity, said: "There was no discussion to start a left party. And it is ridiculous to say we are going to Cope. None of us are even contemplating going that way."
Sources said a "statement by the Gauteng leadership last year, characterising the leadership style of Blade Nzimande as Stalinist" had contributed to the party's decision to suspend the six.
The report also orders the six not to tell SACP members that a policy conference had agreed that the ANC must reserve a quota of parliamentary seats for communists.