"I have not approved parole at this stage," South African Justice Minister Michael Masutha told a news conference.
De Kock was sentenced to two terms of life imprisonment plus 212 years for murder and other crimes as head of a police death squad targeting anti-apartheid activists.
Masutha said a key reason why De Kock would not be paroled was that the families of the victims had not been consulted.
"I am of the view that it is fair and in the interests of the victims and the broader community that the families of the victims are afforded an opportunity to participate in the parole consideration process," he said.
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De Kock is one of a handful of apartheid-era officials prosecuted after being refused amnesty by the Truth and Reconciliation Commission (TRC), which was set up in 1995 to consider amnesty for those who openly confessed their crimes during apartheid.
In chilling testimony before the commission, De Kock turned on his former commanders and returned to the theme in his amnesty application.
"I am the only member of the South African Police Service that is serving a sentence for crimes which I had committed as part of the National Party's attempt to uphold apartheid and fight the liberation movements," De Kock said in an affidavit supporting his parole application.
"I would never have committed the crimes if it was not for the political context of the time, and the position I was placed in, and in particular the orders I had received from my superiors."
De Kock, a bulky man with a hooked nose and prominent chin, was commander of the Vlakplass "counterterrorism" unit, based on a farm in the outskirts of Pretoria, from 1985 to 1993.
Testifying before the TRC in 1996, the highly decorated former colonel described the inner workings of the unit, blamed for killing at least 70 people.