Public protector Busisiwe Mkhwebane has defended her probe into public enterprises minister Pravin Gordhan's conduct in relation to an early pension payout to former SA Revenue Service senior official Ivan Pillay, saying the probe was at a "preliminary stage".

In her statement in response to a letter from Gordhan's lawyer, Tebogo Malatji, she reiterates that he did not respond to the allegations against him as she had requested.

This is after Malatji said her comments that Gordhan had not responded to her was "simply deceptive, false and incorrect".

Malatji said it was Mkhwebane who had not responded to Gordhan when he wrote to her requesting further information on the investigation she was conducting against him.

Mkhwebane responded in a statement yesterday to allegations that the timing of her probe and her conduct raised questions about whether she had an ulterior motive.

Gordhan is facing an onslaught from allies of former president Jacob Zuma, who have now been joined by the EFF in taking on the minister, in a move reminiscent of the 27 questions he was sent by the Hawks on the eve of delivering the 2016 budget speech.

Confirmation of Mkhwebane investigation came days before he was expected to give evidence at the commission of inquiry into state capture, currently underway in Parktown.

Mkhwebane denied that revelations over her investigation were aimed at coinciding with Gordhan's appearance before the state capture inquiry, saying this was false as she had subpoenaed him 20 days before finding out he was expected to appear before the Zondo inquiry.

Gordhan is set to appear before Mkhwebane tomorrow after he was subpoenaed to do so. Mkhwebane said in a statement yesterday her office was empowered to conduct a "preliminary" investigation in order to "determine the merits of complaints, allegations or information".