Maimane warned that if any candidate was found guilty of intimidating opponents they could be disqualified from the race.
His comments came as some DA leaders and members have alleged that some members were being threatened or bullied into not supporting certain candidates.
Processes in the run-up to the February 3 congress have been fraught with difficulties.
The Mercury understands a brawl nearly broke out at a constituency meeting in Newcastle on Saturday as tempers flared between supporters.
In another instance in Pietermaritzburg some councillors claimed they were threatened not to attend a gathering convened by Dean MacPherson, who is contesting for the position of provincial chairperson.
While no official complaint has been laid with the party, some party leaders have taken to social media to highlight what they see as foreign conduct in the party.
Last week DA councillor Christopher Pappas took to Facebook and lamented: “Tonight one could feel the tensions and intimidation that people are experiencing. Delegates and members sharing their experiences of how they are threatened and bullied.”
This was believed to be in reference to the upcoming DA conference, but Pappas could not be reached for comment on Sunday.
In what was believed to be another reference to the upcoming congress, former DA KZN leader Sizwe Mchunu also expressed comments on Facebook at the weekend.
“It seems we are contaminated or infiltrated by foreign tendencies. Threats and intimidation tactics appear to be the order of the day,” Mchunu wrote.
Speaking in Ntuzuma on Sunday, Maimane said the DA did not approve of any threats or related conduct. He said those who had information of such conduct should report it to the party.
A number of DA leaders, who spoke on condition of anonymity, said they had been threatened.
“There has been a pattern of these things. If we were talking of one or two people then we could dismiss it but there have been a number of people who have come forward with these allegations and it is concerning. Obviously, people are scared to report this for fear of victimisation,” said the leader.
The party’s provincial leader Zwakele Mncwango, who is seeking a second term as provincial leader, said he had not formally been made aware of the complaints.
“If people make allegations which are damaging to the DA brand on Facebook but fail to provide any proof then we will have to act on that.”
Mncwango said the party’s rules and regulations were clear that there could not be any negative campaigning against fellow party members in internal contest.
Meanwhile, former DA leader Tony Leon will be in Durban on Monday afternoon as part of Macpherson’s campaign.