"The amendment, as proposed, would make the provincial leaders players, coach, referee, captain and selector, all simultaneously," the letter said. "[It would] enable a provincial leader to entrench a loyal support base by rewarding a network of key lieutenants, regardless of any objective criteria or suitability to serve."
However, the proposal has the support of other provincial leaders - Nqaba Bhanga of the Eastern Cape, Zwakele Mncwango of KwaZulu-Natal, Patricia Kopane of the Free State, Andrew Louw of the Northern Cape, Jacques Smalle of Limpopo, Jane Sithole of Mpumalanga and John Moodey of Gauteng.
Selfe's supporters say a conservative group of white leaders in the party are continuing their attempts to limit the powers of black people in key leadership positions.
"It has been an anomaly not to have provincial leaders serving full-time on the selection panel, particularly in their respective provinces, and it's about time this is corrected," said a DA insider who did not want to be identified.
"So people are opportunistically using this to attack James because they are looking for everything to justify using him as a sacrificial lamb for the [De Lille] mess."
The spat follows one at the party's national congress in April, where Maimane proposed an amendment that would commit the DA to reflecting the country's diversity in its own ranks. Some of the members of the group of 34 said this would amount to a quota system.
Selfe had not responded to questions by the time the Sunday Times went to press.
DA spokesman Solly Malatsi said the party's federal executive had appointed a subcommittee "to work on a proposal for provincial leaders to play a role on selection panels ... consistent with the constitution of the party".