ds's dad driving him without a car seat

[ridiculoussingle]

ds told me today - 'sometimes daddy drives me without my car seat'.
Ds is 5.

I called him (we are separated), and he tried to minimise it - admitted he'd done it, but that it wasn't far, its's only happened a couple of times. He said he'd try to always remember it from now on.
Totally minimised how important it was, even though I told him that they stop the seat belt going round his neck and if he crashed he would be killed.

What would you do? Obviously, I am not there when ds is with his dad, so I can't check. and I think his dad will now say 'don't tell your mum'.

[Dordeydoo]

Has he got a carseat for your son?