"The minister gave written reasons to Mr Derby-Lewis on 4 November 2011," the protector's spokesperson Kgalalelo Msibi said.
She said the protector received an anonymous complaint and after that Gaye Derby-Lewis, his wife, also approached the protector.
There were discussions on November 3 with the legal adviser of the minister, Nosiviwe Mapisa-Nqakula, followed by the November 4 communication.
The Public Protector would now talk to the minister on Derby-Lewis's medical treatment, as this was part of the complaint to the protector.
On Thursday Mapisa-Nqakula's office said she was waiting to hear from the protector regarding the medical parole, and said Derby-Lewis had never applied for medical parole before.
Derby-Lewis, leader of the apartheid-era Conservative Party, and an MP, was sentenced to 25 years in prison for his part in the murder of SA Communist Party secretary general Chris Hani in 1993. He arranged a firearm for triggerman Janusz Walus, who is serving the same prison term.
Both were initially sentenced to death. This was commuted to life in prison after the abolition of the death penalty.
Derby-Lewis, 75, is being treated for cancer.