The credibility of Nelly Yoa, the South Sudanese-Australian man who said the recent violence perpetrated by youths of African appearance made him "ashamed and embarrassed to call (himself) Sudanese" has been questioned by leaders in his community.

Mr Yoa wrote for Fairfax Media on New Year's Day that there was "a major issue among young South Sudanese people in Melbourne" and called on Victoria Police, Premier Daniel Andrews, the state government and South Sudanese community leaders in Melbourne to do more to prevent the violence.

Nelly Yoa has been outspoken about violence in the South Sudanese community. Credit:Daniel Pockett

He claimed he "personally knows and mentors members of youth gangs in and out of prison". His views were widely applauded and he was subsequently interviewed by a wide range of media outlets.

However, the South Sudanese Community Association in Victoria chairman Kot Monoah and spokesman Richard Deng told Fairfax Media they doubted Mr Yoa had worked or currently worked with troubled South Sudanese youths.