South African Prime Minister Pieter W. Botha named Interior Minister Alwyr Schlebusch yesterday as a temporary replacement for former black affairs minister Cornelius Mulder, leaving the door open for Mulder to regain his post if cleared of responsibility for alleged corruption.

Meanwhile, secrecy surrounding a Botha-appointed commission to investigate those allegations of financial and political corruption has been widely attacked not only by opposition parties, but by influential newspapers of the white Afrikaners who control the government.

Die Transvaler, regarded as the official mouthpiece of the ruling National Party, lamented that "the impression could be created that the cards are not going to laid on the table . . . Any shadow of suspicion about a coverup must be eliminated."

In addition, Botha's decision to put an end to any futther probing of the scandal, involving the information department that Mulder once headed, by Judge Anton Mostert triggered widespread indignation. Mostert released sworn testimony on the subject.

All three actions by Botha are creating unease that the recently elected prime minister has decided to prevent the full disclosure of the alleged use of tax funds to set up a pro-apartheid newspaper here and to finance other questionable projects.

Botha also issued a harsh warning to the press, accusing it of publishing "one-sided evidence without hearing the other side of the story." He was referring to the testimony released by Mostert. Botha implied that he might reintroduce a bill to circumscribe press freedom.