I'll explain with an example.
DS (2.5) was playing with his baby sister's stacking cups. I was sitting on the floor with him, DH on the sofa on the laptop. Ds tipped up the cups so they went all over the floor. I said, in a normal voice, "DS can you pick those up please?". DH immediately came in with (stern voice) "DS, pick the cups up"
Similarly, at bathtime, DS was playing with some bathtoys in a way that meant they kept falling off the edge of the bath onto the floor.
Me (who had been present throughout): "DS, stop it please"
DH (who had just walked in): "DS, if you do that again you're getting out of the bath"
I find this really irritating. It feels like DH doesn't trust me to deal with a situation by myself which is ridiculous as I'm at home all day with the dc on maternity leave.
Or does he think he's 'backing me up'?
If roles are reversed, I never wade in when DH is the one doing the telling. I back him up by continuing to reprimand the same behaviour, iyswim, but I don't give an additional "no" for each instance.
How does it work in your house?