csa and household income

Rmcc78

why are the csa allowed to take into consideration partners income and benefits when working out child maintenance when the spouce is not blood related to his children?
My spouce is being hounded for payments and our tax credits are being used as income when we have two of our own children to bring up who are under age 5? is there anyway around this rule?

PreludeForTimeFeelers

Tax credits are awarded to a household, so are partly due to your partner's income. Likewise the children that you and your spouse have reduce the amount that is paid to the parent with care, that reduction would be in place whether your children were your spouse's or yours from a previous relationship. It's swings and roundabouts.