The SABC's acting news head Jimi Matthews.
The Times reported on Monday that in the letter there were complaints that journalists were "taken to task" for not giving adequate coverage to President Jacob Zuma.
The letter was unsigned, apparently because the authors feared they would be victimised, and was addressed to the SABC board and acting news head Jimi Matthews.
"The climate of uncertainty and fear has created a state of paranoia in both the television and radio news rooms and has lowered morale," the letter read.
According to the newspaper, it contained allegations that some programmes were cancelled after the content was announced on air, and when talk show guests had already arrived.
Political journalists were allegedly removed from their posts and analysts from their regular shows without explanation.
There were also complaints that stories about expelled ANC Youth League president Julius Malema were "treated differently".
SABC spokesperson Kaizer Kganyago denied to the Times that Matthews or the board had received the note and said the SABC had received no complaints about the issues it raised.
Last month Matthews instructed reporters at the public broadcaster to refer to President Jacob Zuma's Nkandla home as his "Nkandla residence" and not "compound", "homestead" or "any other such term". – Additional reporting by Sapa