South Africa’s Deputy Education Minister Mduduzi Manana has been accused of hitting a woman during a row at a nightclub.
Mr Manana has not formally commented. However, in a recorded conversation, a person believed to be the minister can be heard admitting to slapping the alleged victim.
The government has said it is aware of the assault accusation.
South Africa has one of the highest rates of sexual violence in the world.
Police figures showed that 64,000 cases were reported last year.
A police spokesman confirmed to Agence France-Presse that they were investigating Sunday’s alleged incident.
The minister for women in the president’s office, Susan Shabangu, has condemned the deputy minister’s “alleged violent actions”.
In a statement, she added that she received the news “with great shock and disappointment”.
On the tape recording, which is purportedly a conversation between the victim’s brother and the minister, the person believed to be the minister admits to slapping the victim when she called him gay.
He implies that other people who were with him were responsible for the worst of the violence.
The recording then emerged in the South African press.
Local media report that the row started over who should succeed President Jacob Zuma when he steps down as leader of the governing ANC in December.