The responses here show just why men get away with not paying properly or at all for their children and women are disadvantaged at work after children.
Let’s start from a position that society should be striving for equality.
2 people have sex, in doing so there is a mutual acknowledgement that the women might get pregnant. If you don’t want to have children, then be celibate or double up on contraception, have the snip or get sterilised. No man should ever complain that he has been trapped. Genuine accidents happen with all forms of contraception.
The baby arrives and the parents split up. Who should bring up and pay for that baby? Shouldn’t both parents make an equal contribution. Sometimes that will be one working more and paying more, whilst the other looks after the child.
Usually, it’s the mother who is primary carer and takes the hit in terms of time out of her career.
In the OP’s situation, she worked out her work and custody arrangements around the Ex’s need to have the children at the weekend so his DM could help as he could not cope on his own. A luxury which the OP was not allowed, she had to get on with it.
Now her Ex has decided that he wants another child and will reduce OP’s maintenance for the children. Why should he be allowed to do that? Why does his desire to have another child mean that he shouldn’t pay for the one’s that he has already got? If OP cannot afford to work or has to go on UC because of his decision, is that reasonable?
Is it reasonable that the Ex’s refusal to pay for childcare means that the OP has to get tax credits? Are tax credits really made available so that a man can avoid his responsibilities in the happy knowledge that the tax payer will pick them up for him.
His excuse is that OP’s new boyfriend has more money than him. How nice of the Ex to decide how the new boyfriend should spend his money. And how humiliating for the OP.
Perhaps the OP wants a relationship where finances are kept separate and she pays her way, like an equal. Does the Ex think that the new boyfriend should ‘keep’ the OP? What a pathetic specimen the Ex is if he really thinks that another man should be paying for childcare bills for his children.
In addition to all of this, the Ex wants the new arrangement to start before OP has even moved in with her boyfriend. Can there be any justification for that? It smacks of spite.
And all those posters who say that the OP should be grateful that the spineless man who left her when their mutual child was 6 weeks old has paid more than the bare minimum to date, then please reconsider your views. A man who has to be taken to CMS to pay the minimum for his children is no man at all.