Barnaby Joyce swatted away questions about his affair with a staffer on ABC's 7:30. Credit:ABC Nothing to see here. Except, like a crib and pram and stuff. Yes, it's complicated and ugly and dirty and no one wants regular updates about the sordid behaviour of our elected representatives, who are, after all imperfect like the rest of us. But I smell a rat. Could it be that when a prominent bloke strays it's a cliche, and when a woman does it, it's time to grab some popcorn? History would suggest this is the case. As part of my PhD on female MPs and the media, I trawled through mountains of press reports (50 years worth) about women MPs, and interviewed dozens of press gallery journalists in a bid to understand when and why the convention that private lives of politicians not be reported on was broken. The rationale is usually that it must be in the public interest, have contravened public statements, or impacted their public duties.

In 2002, Laurie Oakes controversially reported a relationship between Cheryl Kernot and Gareth Evans after she omitted the relationship from her autobiography. And the evidence is clear: it was more likely to be broken for women in politics, whose relationships, sexuality and gender rendered them somehow more accessible. The private life convention has often rested on an assumption that men are not affected by love affairs, flings and trysts, while women are. It's a peculiar kind of unconscious bias. When I called former Democrats leader Cheryl Kernot after the news about Joyce broke, she was puzzled. In the 1990s, Kernot was a star; ALP pollster Rod Cameron described her as the "ideal political leader in Australia", and when she moved from the Democrats to the ALP she polled as the person we most wanted as prime minister. She was lauded as a no-nonsense, effective negotiator. "Saint Cheryl", cooed the headlines. But once she moved parties – "defected" – and the halo slipped, stories began to break (One front page read: "Cheryl goes into Labor").

First came a report in this newspaper published about a relationship she had 20 years prior with a former student. In response, gallery veteran Alan Ramsey told me: "If it was a bloke, it would never have been written. Blokes f--- round in their young life, whatever." Journalists, he said, are hardly "holier than thou", "and yet they are throwing the stones – but they don't throw them at the men". Not long after this story broke, West Australian MP Don Randall said Kernot had "the morals of an alley cat on heat". But the biggest story did not come until she had left politics and had written a political memoir. She did not mention her relationship with former foreign minister Gareth Evans, another open secret. Gallery leader Laurie Oakes went straight to print. His reasoning was this: it could place her defection "in a different light", it would help "explain some of her erratic behaviour" and was "a key factor in the erosion of her emotional and physical health". The "distraction and distress", he said, had made her "flaky". Having an affair with a colleague is undoubtedly dangerous and indulgent. Yet there was no actual proof of a causal connection between the bloom and decline of a love affair and Kernot's professional and psychological slump.

But have we seen timelines of male politicians who have had affairs drawn up alongside key decisions, policies, outbursts or failings? No. Exhibit A: Joyce. Today, Kernot says she accepts she had taken a huge risk, which hurt innocent people, and takes responsibility for that. But the lack of proportion in the response to her story remains jarring. Reflecting on the Joyce story, she told me: "I have been astounded and just a little bit angered by the double standards in operation. You have to own your life, but mine involved a consensual relationship between peers where it was the female who was utterly hounded, psychoanalysed, stalked, with huge doses of sanctimony thrown in. And her professional life consequences were affected. Unlike those of her consensual partner." "Of significant interest to me," she says, "was the way journalists revisited the issue with me when I was being interviewed about another topic for a long time after, but not so for Gareth. In fact, when his recent memoir was published covering the period of our relationship and where he did mention my role in the Native Title debate, not one journalist asked him why it was omitted." Male "gravitas" matters, it seems.

She has a point. Evans has received an Order of Australia; she is still fielding calls about their relationship (yes from me, too). She is the scarlet woman; he is the statesman with a blip in his past, not to be mentioned in polite company. To be clear: none of us want grubby, prurient, intrusive reporting into the private lives of MPs. We all make mistakes; history is littered with people who are fools in private and formidable in public. But the anomalies are important. Kernot invited the same kind of peculiar frenzy Julia Gillard did – a heated, uncontained and particularly nasty scrutiny that hinged on likeability, not professional ability, and provided a vivid disincentive for women contemplating a political career. Like Kernot, Joyce took a huge risk. But his was greater. He is the Deputy Prime Minister. He has spoken repeatedly about the importance of a secure heterosexual union, arguing against same-sex marriage while breaking his own vows. He argued against a national cervical cancer vaccine on the grounds it could make young women promiscuous. He featured his family prominently during his byelection campaign last year. In an interview with The Weekend Australian, he revealed he had placed his wife through a strict vetting process, surmising: "No point starting a project you can't see the end of." Except that he was, apparently, then staring at it. When Leigh Sales grilled him about his affair, he swatted it away: "Private", "private, "private". It's a remarkable privilege.

Julia Baird is the author of Media Tarts: How the Australian Press Frames Female Politicians.