Zille has been referred to the commission for being in violation of the party’s social media policy after she claimed in a tweet that aspects of colonialism had been beneficial to those subjected to the system.
Zille has since kept a low profile on social media and Breytenbach said that may be her choice.
“We are busy investigating still.”
While waiting to board a plane to Cape Town last Thursday after spending a week in Singapore and Japan to strengthen tourism and investment relations, Zille tweeted in sequence:
“For those claiming legacy of colonialism was only negative, think of our independent judiciary, transport infrastructure, piped water, etc.
“Would we have had a transition into specialised health care and medication without colonial influence? Just be honest, please.
“Getting on to an aeroplane now and won't get on to the wi-fi, so that I can cut off those who think EVERY aspect of colonial legacy was bad.
“I apologise unreservedly for a tweet that may have come across as a defence of colonialism. It was not.”
Zille's views were slammed with the EFF branding her "a cold-hearted racist".
DA leader Mmusi Maimane tweeted: "Let's make this clear: colonialism, like apartheid, was a system of oppression and subjugation. It can never be justified."
A senior DA member who spoke on condition of anonymity said Zille’s latest controversy was the last straw for Maimane, who was forced to act.
“He had a long time ago asked her to step down as premier, but she refused. But this is the final nail in the coffin.
“She has damaged her legacy, the good work she has done,” said the member.
DA federal chairperson James Selfe had been compelled to act against Zille despite being considered a close ally by many in the party, according to the member.
Zille’s spokesperson Michael Mpofu said Zille was not justifying colonialism and was referring to how the Singaporean people have overcome the past to build a successful economy.