The designer of the Indigenous flag has spoken out against policing the authenticity of Indigenous art.

Harold Thomas has worked in the art world for more than 50 years and says the only truly authentic indigenous art would be ochre colours on bark.

Thomas said it is important not to allow control of what is and is not Aboriginal art to be policed by a non-indigenous body such as the federal government, who is currently conducting an inquiry into sales of “fake” aboriginal art.