"Government and the ANC, through its national democratic revolution, want total control," Naspers chairman Ton Vosloo told the Cape Town Press Club.
"Our free and independent press and media will be facing huge challenges in the not-too-distant future in preserving the very freedom they enjoy to speak out against the erosion of this freedom, corruption and other ills."
South Africa's ANC-led government has been regularly criticised in recent years for attacks on the press, particularly after pushing a much-derided secrecy bill through parliament.
The party, meanwhile, has repeatedly called on South Africa's media to racially transform their ownership.
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But Vosloo said most companies already had significant black ownership.
"All in all, those who complain about transformation should have a good look at the facts," he said.
"My answer to the complaints (is) the ANC does not like a free and independent owned press."
Vosloo worked as a journalist and newspaper editor before joining Naspers management in 1984.
Since then, the company has diversified from print to pay television, e-commerce and mobile services. It generated 62.7 billion rand (USD 15 billion) in revenue in the last financial year.
This is not the first time Vosloo has warned against the ANC.
In 1993, he told the Rhodes Journalism Review the party would turn out as bad as the apartheid government.
"When the real pressures are on, they're going to behave as badly as the Nats (National Party) did," he said at the time. "Never trust a politician. That's my motto.