I know INBU, but he will think I am and I need to not lose my temper and start calling him feckless because that will get me no-where.
The DC need clothes for a school performance. I've asked him to buy dd2 a pair of shorts (she already has a top and I will buy sandals) and dd1 a hat and shirt (she already has shorts and I will need to buy boots)
What I've asked him to buy comes in at about £30 (just shy of, with delivery), which I know is expensive, but when it comes to school things, particularly this event, I'd rather spend £30 on things they'll wear again than £10 or £15 on dress up clothes that will be worn for half a day and forgotten about.
He pays no maintenance, at all. He feeds them at his about once or twice a week. He will often ask me to send toilet roll or milk with them. He no longer does any overnights because the children simply will not stay there, it's only dinner 2x per week max.
It is not wrong to expect him to pay for these things is it?
Give me calm, coherent reasoning to present to him when he starts asking why he should pay for them or how he is meant to afford it.