Tracy Brabin MP is a class act. Following a tide of hate on social media for wearing an off-the-shoulder top in the House of Commons, she tweeted: “I can confirm I’m not a slag, hungover, a tart, about to breastfeed, a slapper, drunk or just been banged over a wheelie bin.”

Notice, if you will, how gendered most of these slurs were: the full kaleidoscope of every crime a woman can commit, across the whole middle section of her life cycle, from having sex to nurturing a child. We cannot, therefore, make a straight comparison between Brabin and her male colleagues, in terms of whose attire is the most policed. Even if the prime minister, say, were to look like he had just rolled in a pile of jumble and stood up, nobody would infer recent sexual activity from it (unless “just got divorced” falls into that category).

But wait … that is what the prime minister looks like; his dishevelment is famous. His hair he ruffles on purpose, but his near-unique ability to bring an aura of chaos to any kind of tailoring must have been born not made. Dominic Cummings, his familiar, is still essaying cold-climate skater chic in formless garments, multiple scarves and woolly hats. On a man in his 30s, it looks like a poignant fear of maturation; on a man in his 50s, it looks actively sinister, as if he is planning for a life lived in tunnels and hedgerows, following the apocalypse he is shortly to trigger.

Yet they all get a pass – even Michael Gove, jogging beside his security detail with the look of a man deliquescing from the inside, gets no more than a raised eyebrow. An honourable exception should be made for David Cameron, who momentarily stepped out of the shadow of the patriarchy to tell Jeremy Corbyn to put on a suit and tie. Otherwise, whatever men wear, they are A-OK with each other.

Women, meanwhile, get a huge amount of flak for their shoes, for their trousers, for their handbags, for their legs. God forbid they should ever sit opposite one another and both have legs. But, most of all, it is the décolletage: right across the benches, from Theresa May to Jacqui Smith, and through the ages, from Nancy Astor to Alison McGovern, any woman not wearing a polo neck has been ceaselessly scrutinised. “It did not seem to occur to drooling male political commentators,” Diane Abbott wrote a decade ago, “that the only reason they could spy any cleavage at all was because the press gallery looks directly down on ministers.”

Personally, I love shoulders but hate asymmetry, so I would like to have seen both or neither of Brabin’s shoulders in the Commons. But none of this is about aesthetics, fashion or preference: it is all the same question that has been plaguing parliament for (almost exactly) 100 years: what are those women doing in here?