He claims he was not asked whether the child was his before Ms Campion's pregnancy was revealed to the Australian public on the front cover of The Daily Telegraph, eventually resulting in his resignation from Cabinet, reports News.com.au.
However, emails reportedly show the paper did ask him this before publishing the story.
The 50-year-old said he physically apart from Ms Campion, 33, for most of the period when the baby would have been conceived.
Mr Joyce confirmed in December last year that he had separated from his wife after winning a by-election in his seat of New England, sparked when he realised he was a dual citizen.
Vikki Campion. Photo / News Corp Australia
His relationship with Ms Campion, a former staffer in his office was revealed in February and then sparked scrutiny of his travel expenses and also claims of past harassment. The controversy resulted in a sex ban on ministers sleeping with staff and a feud with Prime Minister Malcolm Turnbull.
