Australian Deputy Prime Minister Barnaby Joyce has argued against same-sex marriage. (Mick Tsikas/AAP via Reuters)

Until this week, Australian Deputy Prime Minister Barnaby Joyce was probably best known as a staunch opponent of same-sex marriage. As the country considered legalization, Joyce argued that such unions are wrong because marriage is a process “inherently there for the support of, or the prospect of, children” and because “every child has a right, an absolute right, to know her or his mother and father.”

His own marriage was struggling, he acknowledged at the time. But that didn't stop him from taking a stand in support of the traditional family. (Joyce also argued that legalizing same-sex marriage could hurt Australia's cattle trade because business allies in southeast Asia might find the position “decadent.")

Joyce, 50, was one of the sponsors of the national vote on the issue, designed to slow the process of legalization. (Instead, the national referendum found a majority of voters in support.)

Now, though, gay rights activists are questioning Joyce's devotion to his values after it came out that he was divorcing his wife of 24 years for a former staff member who's pregnant with their child. The staff member, Vikki Campion, 33, is a former media adviser and nearly two decades younger than Joyce. The unmarried couple are now living together.

Rumors of the affair have been flying for months, but the story was broken by the Daily Telegraph, which ran a photograph of a pregnant Campion on its cover Wednesday.

Joyce's wife, Natalie, said she was “deeply saddened” by the affair, and that Campion had once been a frequent visitor to the Joyce family home. “This affair has been going on for many months and started when she was a paid employee,” Natalie Joyce said in a statement. “Naturally we feel deceived and hurt by the actions of Barnaby and the staff member involved. ... This situation is devastating on many fronts.”

The Joyces have four daughters together.

In a television interview after the story broke, Barnaby Joyce called the end of his marriage one of the “greatest failures” of his life. He also denied allegations that he used public money to conduct the relationship.

But Joyce's harshest words were reserved for the tabloids that exposed the affair. On ABC-TV, Joyce said, “I can’t quite fathom why basically a pregnant lady walking across the road deserves a front page. ... I think once we start going through this salami-slicing of a private life, where does it end?”

He cautioned Australians against going down the same path as the United States, where politicians' private lives are routinely reported on.

But gay-rights campaigner Rodney Croome pushed back on those claims. “You can’t put the lives of tens of thousands of your fellow citizens under the microscope and then expect to avoid scrutiny yourself,” he told AAP. Croome said the scandal exposed what “traditional marriage” means for Joyce. “It is not a set of standards for heterosexual couples to live up to. It is a euphemism for prejudice against LGBTI people and our exclusion from the core institutions of society.”

Although most Australian politicians have declined to comment on the affair, the country's parliament is considering a ban on relationships between politicians and their staff members. “Good workplace practice includes clear expectations about behavior,” Cathy McGowan, a member of parliament, told reporters.