Kohler-Barnard was cleared on Wednesday of breaching confidentiality related to misconduct hearings against former communications minister Dina Pule.
The investigation, by Parliament’s ethics committee, followed public statements by Sizani that the Democratic Alliance MP violated her oath of confidentiality by posting updates on Facebook during the hearings.
The parliamentary code of conduct enjoins all MPs and staff serving on the committee to take an oath of confidentiality.
“The Democratic Alliance is today discussing with legal representatives what legal action should be taken against Mr Sizani for this defamatory attack on my character,” Kohler-Barnard said.
The African National Congress said the information was published in The Post in August, an allegation the newspaper later denied.
“I have the maximum 5000 friends on Facebook, many of whom are journalists, and as there was never a word about the hearings on my page, nothing was ever published or broadcast on radio or television,” Kohler-Barnard said.
“I consider Mr Sizani’s comments to have been libellous and a vicious personal attack on my integrity and ethical behaviour.”
In a statement issued later on Thursday, Sizani said he remained “unapologetic” about reporting the allegations to the committee.
“Despite the committee’s decision not to find her guilty, we remain firm in our view that the assertions made in the [Post] article suggested possible misconduct worthy of an investigation by the committee,” Sizani said.
He also dismissed Kohler-Barnard’s “bizarre threat” of legal action.
“We will never be intimidated by irrational legal actions from reporting anything we deem improper to the relevant authorities,” Sizani said.
“We are more than ready to meet her in court whenever she decides to pursue the matter.”
In its ruling on Wednesday, the ethics committee said: “[We] considered the matter and dismissed the allegations against Ms Kohler-Barnard.”
The DA MP was on the committee which recommended that Pule be suspended by Parliament for a scandal in which her boyfriend benefited from state funding.