There are certain phrases that make my heart sink. After “Can I be really honest?” and “Mind if I join you, ladies?” the latest to engender a sense of creeping misery must surely be “Facebook motherhood challenge”.

Of uncertain origin, this viral “challenge” demands that mothers post a series of pictures that make them “proud to be a mum” and then tag other women who they think are “great mothers”.

Many of my friends have done this, bouncily posting shots of themselves with interchangeable babies, all of whom look like glow-worms in padded snowsuits, and tagging whole lists of other “awesome mums” inviting them to do the same. And while I fully understand that they have no intention of hurting anyone, that they are simply happy to have their wonderful children, #blessed, #lovinglife and so on, I still want to punch the screen of my computer in whenever a new one pops up.

The most offensive aspect of this is the idea that it’s a “challenge” at all. A challenge is coping with grief when you wish you were dead, or pushing your mind and body to the limit in a feat of superhuman endurance. It’s not posting a few snaps of your toddler and waiting for your friends to type “aw gorgeous hun xxx” underneath. And it’s unclear whether the challenge in question is to prove what a great mother you are, or merely to challenge your friends to prove that they are too.

This insidious idea of motherhood as a beatific vocational calling began with the Virgin Mary, and reached its peak with the Victorian notion of “the angel of the hearth”, when mothers who didn’t have to work, and had nannies and housekeepers and nursery maids rushing about looking after their children, were depicted as celestial beings radiating goodness, their sole purpose on Earth to gather little children to their rustling taffeta bosoms and gently instruct them. These women often died in childbirth, completing their ascent to sainthood in record time. They were not flesh and blood beings, but an idea, created by the prevailing culture, suggesting that mothering was woman’s high and only purpose.

The idea of tagging people you think are ‘great mothers' is as offensive as tagging people you think are great in bed

This explains the derogatory references to spinster aunts – the unfortunate “freaks” who remained childless, whiskered of chin and bitter of manner. Literature is full of these woman, from Lady Macbeth to Mrs Danvers in Rebecca; women robbed of their natural purpose who descend into madness and fury.

But two world wars which required women to go out to work, the pill, and the fight for equality in the latter part of the 20th century meant motherhood became less fetished. That is, until the rise of the internet and the “mummy blogger”. Suddenly, every other Twitter biography had to state its owner was “proud to be a mummy” or a “mumpreneur” who just couldn’t find the right softness of cot blanket, so made them herself from possum fur and appeared on Dragons’ Den. Instagram is full of gently faded bunting and giggling babies feeding strawberries to their shiny-haired mummies, blogs are packed with tips for having a wonderful time with your “angels”, and it no longer seems easy to admit to finding motherhood painful or depressing, or wanting to crack your wailing child over the head with its capriciously flung egg spoon, because the consensus is that you’re #blessed.

‘If you’ve tried for years to conceive and now have a darling laughing baby, it must feel wonderful. But there’s a world of difference between happiness and smugness.’ Photograph: Danny Lawson/PA

Of course, if you’ve tried for years to conceive, and now you have a darling, laughing baby in your arms, it must feel wonderful. But there’s a world of difference between happiness and smugness (defined as “having an excessive pride in oneself or one’s achievements”). Many mothers simply feel inadequate most of the time, and that sense of failure is exacerbated dramatically by others boasting about how easy and rewarding they find it all, from first “latching on” to graduation (“So proud!!”).

There was no Facebook in my son’s babyhood, but if there had been, I’d have steered clear of plastering him all over it and tagging other women who were, in my view, “great mothers”. Firstly, because it doesn’t take a gargantuan leap of empathy to understand that there are many women who wanted children but for various reasons didn’t have them. There are many who have lost children. Equally there are many women with children who are depressed, worried sick about their teenager, or desperately missing their adult child. I’m pretty sure they don’t feel a great deal better when their timeline is full of people boasting about their happy families.

It’s not the casual posting of photos aimed at friends that I mind. It’s the revived fetishisation of motherhood, the idea that it’s a “challenge” that only “mummies” can understand, an exclusive, excluding club of laughing, shiny, breast-feeding super-beings who know exactly how to raise “great kids” and will only invite others of their kind to join the party. In truth, the idea of tagging people you think are “great mothers” is as offensive as tagging people you think are great in bed. How do you know if they are? And how do the ones who don’t get tagged, and see that smug little list of anointed “great mums” feel? If anyone’s judging you as a mother, it should be your children – and nobody else.

Nobody is always a great mum, few people are truly terrible mums, and motherhood shouldn’t be a “challenge” that can be won or lost on the posting of a picture of some kid with banana round his mouth. Yes, it’s just meant to be “a bit of fun”. But in reality, the “motherhood challenge” is simply another way to measure women and find them wanting.