The ABC has been forced to issue an apology for 'mistakenly' providing archival footage and audio to the Yes campaign for their John Farnham 'You're the Voice' TV ad.

The national broadcaster conceded it had violated its own policies in supplying 26 seconds of video and 5 seconds of audio for the campaign.

Last week, Farnham had granted the Yes campaign the rights to his iconic song, in the hopes that it would "change the lives of our First Nations people for the better" and bolster the campaign advocating constitutional change.

The issue was first raised by eagle-eyed social media users and reported on by Independent journalist Rukshan Fernando, who called attention to the story.

"We are updating our licensing processes to avoid this situation in the future," an ABC spokesman acknowledged, describing the error as "regrettable."

Warren Mundine, leader of the opposing No campaign, dismissed the mistake as "a joke." He told The Australian:

"There should be a very, very serious investigation into this. The ABC is the national broadcaster and should remain bipartisan." Mundine called for the Yes campaign to remove the ABC's material, stating:" They were not supposed to be given that stuff. If they're going to be honest about it, then they've got to remove it and hand it back."

The ABC did not comment on whether it would ask for the materials to be deleted, but Mundine argued that the oversight was part of a wider pattern of poor governance by the broadcaster.

"The ABC needs to really, seriously look at some of its procedures and accountability," he added.