THERE'S been a flurry of pictures of Tom Cruise and Katie Holmes's toddler daughter Suri clutching a bottle of milk. One downside of being a celebrity parent is that, should you do something "wrong", a raft of experts surges forward to comment publicly on your misdemeanour. Nothing satisfies more than ticking off a new parent. American paediatrician Dr Charlotte Cowan tells US magazine: "Most paediatricians recommend that a bottle should be given up by age one, and almost certainly by 18 months." Tsk tsk. I know other people's children have a tendency to grow up without you realising - embarrassingly, last Christmas I sent a friend's nine-year-old a Playmobil car-wash, and my daughter received a rattle when she was in primary one - but still. Suri Cruise is two years old. She's not sitting her driving test with a bottle of formula plugged into her mouth.

You don't have to be famous to be ticked off by the waggy-finger brigade. In fact you don't even have to have given birth. Stephanie Calman, who runs parenting website badmothersclub.co.uk, told me about being spotted in the street by a neighbour while she was visibly pregnant and - gasp - carrying a bottle of wine. "Should you ?" the neighbour asked, glancing in an alarmed fashion from bottle to belly. "For all she knew, I was going to a party and taking the wine as a gift," Stephanie raged. "Whatever I was planning to do, it was none of her business."

Things rev up several notches post-birth when there are ample opportunities to point out your incompetence. For a brief period my twin boys attended a playgroup where, I was informed, they were expected to be potty trained. The group took children from two-and-a half years old. I know we'd all like our children to be reliable toileters by this stage, just as we'd like them to sit nicely in cafes without spitting out chips or flooding the table with lemonade. However, you can "expect" all you like - there's actually very little you can do to chivvy them along before they're ready. "Hmm," Playgroup Fuhrer said, sucking in her lips. "I suppose we can take them. But if they soil a nappy we'll phone you and you'll have to come and change them."

"Yes, of course, that's fine, thank you, thank you," I blethered, ridiculously grateful for the prospect of four child-free hours a week. Yet I was also confused. Surely, an unavoidable aspect of working with very young children is occasionally having to deal with their emissions. How could you not expect it to happen? It would be like working in a shop and shrieking in panic when a customer walked in.

Fuhrer's warning made me nervous. While the boys were at playgroup, I paced the house, unable to settle to anything. If the phone rang my heart lurched as I anticipated deep humiliation and the scorn of my peers. At six months pregnant, I just wanted to run a bath and lie in it undisturbed - but what if the poo call came while I was naked and wallowing in suds? How quickly would I be able to get dry, dressed and hare up the road armed with nappies and wipes? What would they do with my children in the meantime? I pictured them being removed from the main play area and kept in a foul-smelling holding zone for un-potty-trained children. As everyone else's kids had clearly been trained for months, if not years, I imagined this as a lonely, desolate place.

Oddly enough, the poo call never came. Perhaps, in a rare moment of kindness, Fuhrer had kitted herself out in an asbestos suit and dealt with the "situation" herself. I didn't dare to ask.

We moved to a different town with a more welcoming playgroup, and our sons entered a new phase of suffering so many minor injuries that our most common outing was to A&E. Those Twins Who Aren't Potty Trained had become Those Twins With The Head Bandages. This was actually less shameful. At least then, I could pretend we were playing doctors.

Fiona's novel, Mummy Said the F-word, is out now (Hodder, £12.99)