Father badmouths mother

[mayflower21]

What to do? Father always involves the child telling DC tell your mother not to shout at me, or to me in front of DC you didn't want them (not true). Just makes up lots of ridiculous stuff. DC is 4, I think they might start believing those things

Are you still with him or is this happening at handover?

If you are still together then I would advise you leave, your DC is being taught that this is how you treat your DP/ mother of your child. it’s horrible for you to be living with that too.
If it’s at handover then I’m not sure what you can do.