He was seated towards the rear of the chamber and smiled as Speaker Baleka Mbete announced that he had been duly sworn in.
Mbete said the vacancy in the National Assembly was due to the resignation of Abram Mudau.
Reports have it that Mudau was ordered to resign to make way for Molefe.
Opposition MPs booed as Mbete made the announcement.
“Where is that corrupt bastard?” asked the EFF’s Moses Mbatha, who was then called to order by an ANC MP. Mbete asked Mbatha to withdraw his remark, but he refused.
“I will recognise your voice in the Hansard recording,” Mbete promised.
EFF chief whip Floyd Shivambu asked Mbete “since when” does parliament’s communication department make announcements on behalf of political parties.
He was referring to a press release by parliament announcing Molefe’s appointment.
“We will not be abused by the Guptas,” said Shivambu.
COPE MP Deidre Carter also made jibes about Molefe.
“True north changed direction in this House because my immorality compass is [pointing] direct to the Honourable Molefe,” said Carter.
DA finance spokesman David Maynier said the fact that the “disgraced” former Eskom group chief executive was sworn in as an MP was a “major escalation in the civil war within the ruling party and the battle for control of the Treasury being driven by President Jacob Zuma.
“We cannot be sure but it will presumably not be long before Brian Molefe is appointed to the finance committee to serve time before being appointed deputy minister of finance with a view to controlling the R1.8-trillion managed by the Public Investment Corporation,” said Maynier.