Senior Democratic Alliance officials have denied that the decision by respected MP Raenette Taljaard to leave parliament next month is as a result of party infighting.
Their comments come ahead of next weekend's national congress in Durban.
Chief whip Douglas Gibson said on Sunday he had known about Taljaard's intention to resign "a while back" and that any suggestions that the decision could be linked to internal conflict in the party was "rubbish".
"Her resignation comes as no surprise and I do regret the fact that she has decided to swap her political career in order to further her studies. But it is merely her personal decision," he said.
According to newspapers, Taljaard's decision to leave parliament partly resulted from a clash with Gibson.
The chief whip said Taljaard had considered leaving the party a few times before.
"There was many an occasion when she considered 'should I or should I not leave the party?'
"I don't think she had a commitment to a long-term political career like most of the rest of us do," Gibson said. Party spokesperson Helen Zille concurred that Taljaard's decision was "not symptomatic of infighting".
She added that there was "absolutely no truth" to claims Taljaard had resigned over the DA's plan on public HIV testing.
The DA's federal executive recently endorsed a three-part HIV and Aids programme aimed at ensuring that the party's MPs and MPLs lead by example in the fight against the pandemic.
Part of the plan is public tests for elected representatives and a decision that they use every public speaking opportunity to deliver a short message on HIV and Aids.
The Treatment Action Campaign has criticised the party's efforts with spokesperson Mark Heywood calling it "opportunism".
On Sunday MP Ryan Coetzee, who helped devise the plan, said he doubted Taljaard's leaving was linked to the programme.
In a brief statement on Friday, Taljaard said she was leaving "for private reasons" and wished the party well.