I posted a thread about being baited in the same way and someone posted that in reacting to it I was encouraging him to amp it up.
For example the sad clown told my 5 year old that we were no longer together because I kissed other men.
I have told her that this is not true and that I didn't understand why he was telling 'stories' (our word for lies).
The other one was where he told her we were still married. I had to explain 'technically' to a 5 year old (say you went swimming and dried off everything but your big toe. If someone said you were wet it would be 'technically' true but you're not really wet, are you? Just your big toe).
Rather than spend my time telling her he is lying I've taken to telling her that it is a difference of opinion. I don't agree with him and he doesn't agree with me. We then spend most of our time talking about her feelings.
I won't lie - it is difficult because the urge is to unleash hell to get him to STFU is strong. To show him how he is damaging them is to try to reason with him.
Unfortunately that course does not and will not work. They are more concerned with taking jabs at us than they are about not fucking up our kids.
TBH I think they believe most of the crap lies they tell these kids.
There's nothing you can say to make him stop. Deal with your kids and their IC, through legal channels if you can.
Unfortunately trying to reason with him could provoke him. Perhaps he won't stop even if you don't take the bait. Remember you can't control the fuckery - you can only control how you react to it.
Focus on your kids and yourself - do what you can via IC and legal channels and remind yourself that taking the bait doesn't do any good.
((ButterflyGirl)) I can't tell you how much I loathe this aspect. The accusations and claims he makes are outrageous and enormously damaging IMO. Unfortunately it is not against the law to be a shit parent.
Divorce cures the shit husband problem but not the shit father problem.