Mandla Nkomfe, the ANC's chief whip in the Gauteng legislature and the party's deputy secretary in the province, is the latest senior member of the ruling party to face allegations of sexual harassment.
On the eve of the 16 Days of Activism Against Women and Child Abuse, Nkomfe has become the third top ANC man to face such allegations.
Last week, parliamentary chief whip Mbulelo Goniwe was "given leave of absence" after allegedly sexually harassing a 21-year-old parliamentary administrative assistant.
A former South African ambassador to Indonesia, Norman Mashabane has charges of sexual harassment pending against him.
Mashabane started work this week as a political advisor to Limpopo premier Sello Moloto.
Sources allege that Nkomfe fondled a female party member and worker in the legislature building and told her that they should have sex so that she could advance her political career.
The woman is said to have asked Nkomfe about the vacant position of deputy chief whip of the party in the Gauteng legislature.
She complained of sexual harassment to the ANC and the party caucus was told of her allegations on Wednesday. A team was instructed to investigate, report to the party and recommend action.
The complainant refused to be interviewed yesterday but said: "I am consulting a doctor and do not want to talk about this issue."
She referred calls to the ANC.
ANC spokesman Hope Papo was not available for comment.
Nkomfe, who was head of the 12-member South African observer mission in Somaliland last year, praised the women of that country and decried the marginalisation of women as political candidates.
"We were all heartened by the high turn-out of voters, particularly women, despite the small number of women candidates," he reportedly said.