Joburg mayor Herman Mashaba has referred the head of the hawks, General Berning Ntlemeza, to the Independent Police Investigative Directorate (IPID) for investigation, according to a Business Day report.
Mashaba reportedly met with IPID head, Robert McBride, to notify him that he had evidence to suggest that Ntlemeza had interfered with investigations brought to the Hawks by the City of Johannesburg.
Mashaba said: "Subsequent to the appointment of [former Gauteng Hawks head, Shadrack] Sibiya and the anti-corruption unit in the city, there's been a substantial increase in the number of cases investigated and referred to both the SAPS and the Hawks."
But, he reportedly said the ratio of cases investigated to those opened was small.
Hawks spokesperson Robert Netshiunda told Business Day it was wrong of Mashaba to "venture into the realm of policing without invitation".
The move is likely to further increase tensions between McBride and Ntlemeza, who are already investigating each other.
McBride was asked by the Hawks to provide them with a statement related to the deportation of Zimbabwean nationals 10 years ago. He declined to do so after receiving legal advice.
The Hawks told McBride to stop with "mud-slinging" and the spreading of "misinformation".