Underlying tensions within the Democratic Alliance have flared up following Parliamentary Leader Lindiwe Mazibuko's announcement that she would be stepping down to study for a Master's in Public Administration at Harvard University's Kennedy School for a year.

The Sunday Times reported that Mazibuko had applied for the position in September last year, and had learnt that she had secured a scholarship for the course, about two weeks' ago. The newspaper reported that Mazibuko had informed party leader Helen Zille "at her official residence, Leeuwenhof, in Cape Town at 5pm yesterday [Saturday]. The two met for about an hour." This was after she had told the newspaper's Jan-Jan Joubert of her decision.

The Sunday Times report quoted Mazibuko as saying "I had considered it before, and believe the decision is the right thing at the right time for the DA and for me, because it will improve what I can offer the DA politically" and Zille as stating: "I am saddened by the decision because Lindiwe is a talented politician, but I agree sometimes in one's career one must take time out to consolidate oneself and one's skills." In the article Mazibuko again denied long-standing rumours of a breakdown in her relationship with Zille.

However, the long running resentments and tensions between the Zille and Mazibuko camps within the DA were exposed in an intemperate exchange on the BDLive website between former and current DA staffers. On Sunday BDLive columnist and former senior DA official, Gareth van Onselen, tweeted that his piece the following day would be on the "real reasons Mazibuko left the DA."

My @BDliveSA column tomorrow: "The real reasons Mazibuko left the DA". I would recommend you look out for it.

— Gareth van Onselen (@GvanOnselen) May 11, 2014

Zille responded:

@GvanOnselen @BDliveSA After yr tweet, I called @LindiMazibuko to ask if I had missed anything. She stressed she gave me the REAL reasons.

— Helen Zille (@helenzille) May 11, 2014

Business Day journalist Carol Paton commented:

@helenzille @GvanOnselen its really never advisable to give the real reason you leave a job.

— Carol Paton (@politicsblahbla) May 11, 2014

To which Zille replied:

@politicsblahbla @GvanOnselen It is, if you wish to return and be trusted. I trust Lindiwe gave me the full and REAL reasons, as always.

— Helen Zille (@helenzille) May 11, 2014

Asked by one person on Twitter "What did you ever do to Gareth, seems he is after your blood?" Zille responded:

@ChiefThabo I didn't give him the job he wanted. That simple.

— Helen Zille (@helenzille) May 11, 2014

Van Onselen's column was posted online on earlier Monday morning by BDLive and then subsequently pulled down for editing, before being posted again later that day. The question posed by Van Onselen was this: "The loss to the DA and South Africa is profound. Mazibuko was a superstar. How is it that the DA has come to lose someone who embodied all its best qualities?"

He argued that the internal environment within the DA under Zille's "dominant and authoritarian" leadership had become toxic, with a deep divide having opened up between Zille and Mazibuko, and the party's staff taking sides in the resultant internal factional battles. Van Onselen wrote:

"It appears from discussions with DA members that Zille had placed a party staffer loyal to her [Gavin Davis] in charge of all parliamentary communication (an example of DA cadre deployment, the elected parliamentary leader of the opposition could not sign off the communication of her own caucus). The relationship between those two became entirely politicised, with the head of communications, a staff member, relentlessly undermining Mazibuko's communication and denuding those platforms available to her of their worth. Certainly they deteriorated to the point that they were irreconcilable. Mazibuko's staff have been systematically isolated and marginalised inside the party. Zille's faction no doubt leaked correspondence to the media about the DA's affirmative action foul up, damning Mazibuko....

Mazibuko was sidelined out the DA's election campaign, reduced to a bit player on posters, adverts and party events. It is true Mazibuko was sick for some of this time, but these kinds of decisions are made months in advance of the actual campaign. In her place, a golden highway was paved for Maimane, Zille's heir apparent and the ultimate yes-man. The party's Gauteng campaign was used to create a platform for his progression and he will now, inevitably, be anointed parliamentary leader - the first time a DA politician has become parliamentary leader without ever serving in parliament, testament to Zille's inability to maintain unity in her own caucus."

In his reply, published on BDLive on Tuesday, Davis suggested that Mazibuko had stepped down out of fear of losing the party leadership to Maimane. He also suggested that Mazibuko may have had a hand in Van Onselen's column. He wrote: "Lindiwe Mazibuko's proximity to Van Onselen is well known. It is highly unlikely that he would not have consulted her on his column before it was published. And, at the time of writing, she had not refuted his claims. So let me take the opportunity to set the record straight."

Davis concedes while Mazibuko and Zille's relationship did become "strained towards the end", though not irretrievably so, this was not a result of the latter's authoritarianism. He writes:

"When Mazibuko was elected parliamentary leader, she insisted on having her own, expanded staff complement. She had her own platforms and carte blanche to position herself as the counterpart to the president of the republic. Zille strongly encouraged this, and ensured she had every opportunity to build her profile.  Mazibuko was given ample space to lead the caucus as she saw fit, immediately reshuffling the shadow cabinet and making subsequent changes without consulting the party leader, as is the convention. This generated strong resentment within the caucus. If anything, Zille was criticised for being too "hands off" in her dealings with the parliamentary management team. This was brought into sharp relief with the Employment Equity Bill debacle. The fact is that Mazibuko ignored advice on how to deal with the bill, which is how we ended up in the embarrassing situation that we did."

On Van Onselen's allegations against him personally Davis commented:

"It is ironic that Van Onselen refers to my appointment as communications director at the DA as "cadre deployment" when he himself had been deployed to that position prior to me. Zille had nothing to do with my appointment. I applied for the job when the position became vacant and I was interviewed by James Selfe and Jonathan Moakes. Furthermore, when I was appointed, Athol Trollip was the parliamentary leader, not Mazibuko. It is therefore false to insinuate that I had been sent to Parliament to exert control over Mazibuko. I arrived in August and she was elected in October.

The first task I set myself was to repair the damage wrought by Van Onselen - my predecessor - in his internal war against Trollip. This had started when Ryan Coetzee, Van Onselen's mentor, lost the election for parliamentary leader against Trollip. That particular battle had caused deep divisions in the caucus and created a culture of mistrust between MPs and staff. My next job was to professionalise communication in Parliament and align it with the rest of the party. This entailed a restructuring process and filling the numerous vacancies that Van Onselen had simply not bothered to fill.

Like Van Onselen before me, I was empowered to sign off all party communication (including Parliament). This was not new. It was done in terms of a system designed by Ryan (Coetzee) and enthusiastically implemented by Van Onselen when he was in that position. As time went on, I delegated this responsibility more and more to other staff members. When it came to Mazibuko's office, I rarely signed off on any of her communication, leaving that to her chief of staff."

Davis further denied that Mazibuko's staff had been "isolated and marginalised within the party" and that Mazibuko "was shut out of the election campaign." He noted that not only had Mazibuko been "on sick leave for six weeks of the campaign" but that, earlier, she had been the "first in our party to be asked to avail herself for the nomination of Gauteng premier candidate. She declined, later telling people that she turned it down because she saw it as an attempt to ‘sideline' her. Had Mazibuko been chosen as the Gauteng premier candidate, the same resources would have been put behind her. The decision to focus on Gauteng was a strategic one taken by party structures on which Mazibuko sat, and agreed; it had nothing to do with who the candidate was or any future internal elections. To say otherwise is paranoid and delusional."

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