Barnaby Joyce's ex-wife has broken her silence on her husband's extramarital affair, saying she believes the former deputy prime minister is on the verge of a breakdown.

Natalie Joyce has also hit out at her estranged husband and his new partner Vikki Campion for their paid television tell-all interview, labelling it an "absolute disgrace".

Mr Joyce has previously pinned the interview on Campion, saying it was her idea, which Mrs Joyce told the Australian Women's Weekly did not surprise her.

"I wasn't surprised she sold their 'exclusive' story, and certainly not surprised the $150,000 went to her child, but it begs the question, if Barney agreed to be a part of it, how could he allow his four girls to be overlooked?" she told the magazine.

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"In saying that, I wouldn't want a cent of that money. It was all we could do to watch it without throwing a brick at the TV!"

Describing herself as a normally a very private person, Mrs Joyce said she was speaking out because she felt the need to stand up for herself.

"They thought I would lie down, but this time I couldn't," she said.

"I'm doing this so the girls feel empowered, and know their mum stood up and defended our fine name."

The mother of Mr Joyce's four daughters — who was not paid for her interview — also said she believes the former deputy PM is on the verge of a breakdown.