In one of the letters, dated March 19, Hospersa chair Anneline Fry told Mbengashe about "intolerable working conditions, ongoing tireless victimisation and making up of false statements against white managers".
The hospital's operations manager, Stafford Allan Fry, has opened a criminal case with the Equality Court against Nehawu branch chair and former employee at the hospital Thando Mtshalala for using hate speech.
Anneline Fry told Mbengashe that her husband was left with no choice but to approach the court due to lack of action from the department of health's provincial head office.
In February, Stafford, in his approach to the Equality Court, also demanded R200000 for defamation .
Both Frys, in their letters and in the court application, called Mtshalala's behaviour "vile" and "abusive".
Mtshalala resigned on Friday but when he was approached for comment on Monday, he said: "I have been advised by my lawyer not to talk about this matter because it is in court."
He also refused to divulge his lawyer's details.