EFF leader Julius Malema says his party will approach the courts should Finance Minister Nhlanhla Nene "lie" under oath during his testimony at the commission of inquiry into state capture.
Nene is due to testify on Wednesday at the commission chaired by Deputy Chief Justice Raymond Zondo.
"He must answer honourably. Otherwise, we will approach the court for perjury," Malema told News24.
The finance minister is expected to share details of his 2015 axing by former president Jacob Zuma in December 2015, during his first stint as the head of Treasury.
Nene will also be expected to shed light on his own relationship with the infamous Gupta brothers. On Tuesday, the Business Day reported that he had held several meetings with the family during his first term in office, and while he was deputy finance minister.
The EFF, in a statement also released on Tuesday, raised concern over Nene's refusal to answer questions the party had posed to him in May 2018 about his relationship with the Guptas. It accused the minister of going against parliamentary rules and practices, which oblige members of the executive to truthfully and consistently answer questions posed to them by MPs.
The Guptas have been placed at the centre of the state capture project, with the commission investigating allegations of undue influence by the family on Zuma's administration.
"The reason Nhlanhla Nene was appointed as minister of finance by a captured Jacob Zuma was because he worked with the Guptas," the EFF statement said.
The party also claimed that the reason former deputy minister Mcebisi Jonas and former finance minister Des van Rooyen were approached by the Guptas was because Nene had stopped taking the Guptas' phone calls and had tried to work independently of the family once he became minister.
In June while addressing Parliament, Malema asked who had recommended Nene for the deputy minister post, telling other MPs that Nene was "not the type of guy we think he is" and that he was "corrupt as hell".
When asked if he would approach the Zondo commission should Nene's testimony be at odds with the information and evidence the EFF claims to have access to, Malema responded: "Absolutely."
During his parliamentary address, Malema said he had the time, minutes and venues where meetings took place.
"The EFF is aware of many other dealings and dark secrets that compromise Nhlanhla Nene," the party's statement says. It promised to "reveal all" if he does not step down as finance minister.