The Democratic Alliance on Monday said it was considering launching a legal bid to overturn President Jacob Zuma's appointment of Willem Heath as the head of the Special Investigating Unit (SIU).

On Sunday, the City Press newspaper quoted Heath saying former president Thabo Mbeki was responsible for the charging of Zuma's former financial advisor Schabir Shaik with corruption.

He also claimed Mbeki initiated rape charges against Zuma.

Zuma was acquitted of rape, while Shaik was convicted of bribing Zuma in relation to arms deal contracts.

The DA's Debbie Schafer said Heath's comments were problematic.

"I do find it very strange and quite unacceptable," she said.