Actor Josh Duhamel and his pop star wife Fergie have to watch where they step at home as their son Axl struggles to get to grips with potty training.

The Transformers star reveals 18-month-old Axl has started to follow dad into the bathroom whenever he has to pee, but his toilet habits are far from sanitary.

He says, "I don't know if this is bad parenting on my part, but (I'll say), 'Ok, I'm gonna go pee pee' and then he runs in and he loves to watch. He puts his hands right on the urinal and I'm like, 'Don't touch that...' He loves to watch me pee!"

The couple has since started to give the boy lessons on how to properly use the toilet, using a little step-up aid, but Duhamel admits Axl has has yet to actually hit the target.

The actor continues, "He crawls up on it (the steps) and he (stands there) so he knows exactly what to do, but he doesn't pull the trigger. And then you turn your head for one second and he's peeing on the carpet... But he's getting it; he's starting to get it."