The deputy prime minister and Nationals leader also denied misbehaviour allegations reported by News Corp and Fairfax Media and reserved his right to sue for defamation.
“I would like to say to Natalie how deeply sorry I am for all the hurt this has caused. To my girls, how deeply sorry I am for all the hurt it has caused them,” he told reporters outside federal parliament on Tuesday.
“To Vikki Campion, how deeply sorry I am that she has been dragged into this.
Later in a written statement, Joyce said his marriage was under pressure for some time.
“Natalie and I tried to make it work again in April last year but it subsequently came to an end,” he said.
“This has been a searing personal experience for Natalie, our daughters and for Vikki – criticise me if you wish but please have some regard for them.”
He also apologised to voters in his New England electorate for “this personal issue” going public.
Joyce’s leadership is under pressure after his relationship with Campion was publicly exposed last week and questions were asked about her job transfers.
Campion went to work for Joyce in August 2016.
“A friendship subsequently developed and that became, over time, more,” the Nationals leader said.
But he denied breaching the ministerial code of conduct, which says frontbenchers cannot employ “close” relatives or partners or get them work in other ministerial offices “without the Prime Minister’s express approval”.
Campion moved from Joyce’s office in April to work for Nationals MP and cabinet minister Matt Canavan, and then to the office of then-Nationals whip Damian Drum after Canavan stepped down following questions over his citizenship.
Joyce said he was “very aware” of the rules.
“It is without a shadow of a doubt that Vikki Campion is my partner now,” he told said.
“But when she worked in my office, she was not my partner. When she worked in Matt Canavan’s office, she was not my partner. And Damian Drum was not a minister.”
Drum said on Monday he was told at the time Campion came to work for him it was no longer “an ongoing affair”.
The Daily Telegraph reported on Tuesday Prime Minister Malcolm Turnbull told MPs in August he’d been reassured by Joyce the “affair was over”.
In December, Joyce told parliament his 24-year marriage to Natalie Joyce had broken down.
His child with Campion is due in mid-April.
Joyce also denied the allegations, which have also been circulating on social media, he misbehaved at an awards ceremony for rural women in 2011.
“This is a story that has been brought about by a person unnamed, at a venue unnamed, at a time unnamed, seven years ago, and has been peddled by the bitterest of political enemies to me,” he said.
“It did not happen.”
Labor said Joyce’s position in the government – he will be acting prime minister next week when Turnbull is overseas – was becoming “increasingly untenable”.
Finance Minister Mathias Cormann offered support to Joyce as a “valued friend and colleague”.
“Barnaby is big and ugly enough to explain himself,” he told reporters.
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