Nationals heavyweight John Anderson has emerged as a high-profile ally of a group leading the campaign opposing an Indigenous Voice to parliament, as speculation ramps up over who will lead the official No campaign.

The former deputy prime minister, who chaired a Recognition review panel for the Abbott government in 2014, said he was considering the role he would play in an outfit former ALP president Warren Mundine is setting up that will function as the peak body co-ordinating the No campaign.