Mandela memorial: Outcry over 'inept' sign interpreter 11 December 2013 Last updated at 12:14 A language interpreter signs tributes by Nelson Mandela's grandchildren The Deaf Federation of South Africa told the BBC the man's signs were "arbitrary" and "did not make sense." Wilma Newhoudt-Druchen, South Africa's first deaf female MP, tweeted that the interpreter was "signing rubbish." She told the BBC the man was "employed by ANC head office or used by them" but didn't use South African sign language. ANC-linked interpreter on the stage with dep president of ANC is signing rubbish. He cannot sign. Please get him off," she tweeted during the live broadcast. The ANC refused to comment on whether it had used the interpreter at previous events. South Africa's government said it was preparing a statement, according to the Associated Press news agency. Making a mockery The sign language interpreter has yet to be publicly identified. Francois Deysal, who is a signing trainer at the Deaf Federation of South Africa, said he was "not known to the deaf community or other interpreters in South Africa." South African sign language has its own structure and is not linked to any spoken language like Afrikaans, Xhosa or English, Mr Deysal told the BBC's Newsday programme. South African Braam Jordaan, the Young Deaf Leader for the World Federation of the Deaf, told the BBC the man was "creating his own signs." He said deaf people had been excluded in South Africa long before apartheid happened. There is one sign language interpreter for every 10,000 deaf people in South Africa, he said via an interpreter. The BBC's See Hear researcher Erika Jones, also a sign language user, said the man's signing seemed to have no grammatical base and kept repeating sign patterns when it was clear that the speaker was not using repetitive words. Major national and international news channels broadcast Mr Mandela's state memorial service live on Tuesday. The man was seen on stage signing as friends and family of Mr Mandela, and world leaders, paid tribute to the former South African president. UK deaf news blog The Limping Chicken said the sign language interpreter had a "strange repetitive rhythm to his movements," and "the structure of his hand and body movements didn't seem to change no matter what the speaker was saying." Blog editor Charlie Swinbourne said the man "made a mockery of our language." If the accusations that the man was a "fake" turn out to be true, "on a day when the world saluted a man who fought oppression, a guy stood on stage and effectively oppressed another minority - deaf people," Mr Swinbourne wrote.