Partner (over a year together) moved in recently and is contributing more financially than I am (I have three children by previous partner). He said this was fine as we both contributed mine was just significantly less as I work parttime. However now he's decided his contribution is too much and I need to work more, which I'm not happy with as I've only just made the move to part time work as I've worked full time for a long time. He knew this for a long time before he moved in. He's unhappy contributing this much as he has debt due to previous relationship, and also keeps comparing it to how when he was single he would have more money. I have significantly less money as I no longer claim any benefits apart from Child Benefit, and I'm now running into debt because of the situation.
Is there situation where a couple can claim tax credits as if they were single if other children are involved? I'm pretty sure there isn't but I wanted to check as it boils down constant arguments over money.