Owners of Mandela 'fake' interpreter firm 'vanish'
Hendrietta Bogopane-Zulu apologised to the deaf community for the poor quality of interpretation given by Thamsanqa Dyantyi from SA Interpreters.
"He is Xhosa speaking. The English was a bit too much for him," she said.
Mr Dyantyi himself has blamed his flawed interpretation on a schizophrenic episode.
He also admitted he has been violent in the past.
During the memorial, Mr Dyantyi was employed to stand on the stage next to key speakers such as US President Barack Obama and Mr Mandela's grandchildren, translating their eulogies.
But the minister denied there was a security issue, saying the interpreter had been properly accredited.
Mr Mandela died last week at the age of 95, and will be buried on Sunday.
His body is currently lying in state in Pretoria, with thousands queuing to pay their respects.
'No embarrassment'
Ever since Tuesday's event, pressure has been mounting on the government to explain why Mr Dyantyi was hired for such an important event.
During a press conference, Ms Bogopane-Zulu, the deputy minister for women, children and people with disabilities, admitted that a mistake had been made but said there was no reason for the country to be embarrassed.
"There are as many as a hundred sign language dialects," she said, to explain the difficulties he faced.
"He started well and later he became tired. Guidelines say we must switch interpreters every 20 minutes."
She did not rule out employing him in some circumstances again.
But she accused Mr Dyantyi's employers, SA Interpreters, of being cheats, and said the company's directors had now vanished into thin air.
Mr Dyantyi's performance was watched on television by millions of people worldwide.
He said that during the event, he had lost concentration because of voices in his head.
He said he had started hallucinating, and saw angels coming into the stadium.
"I was in a very difficult position," he said.
He also indicated that his past behaviour had sometimes been unpredictable, telling the Associated Press news agency that "sometimes I will react violent on this place, sometimes I will see things chasing me".
Mr Dyantyi's performance at the memorial provoked anger among South Africa's deaf community.
During the broadcast, Wilma Newhoudt-Druchen, the country's first deaf female MP, tweeted: "ANC-linked interpreter on the stage with dep president of ANC is signing rubbish. He cannot sign. Please get him off."
It appears that Mr Dyantyi has worked for the ANC before, as footage from two big ANC events last year show him signing on stage next to President Jacob Zuma.
The South Africa's Translators' Institute said there had been complaints over Mr Dyantyi's work before, but the ruling party had taken no action.