The other woman

My partner had to start paying csa in Dec 10. He has always paid for his child and saw him regular but csa decided to start deducting the amount as ‘they wasnt aware there was something in place’. we have both always worked, i receive no income from my kids father and the csa are taking everything from my partner except 135 a week. this does not comply with the letters that state they will take 90 (including back payment), this week they took 160. How are we expected to carry on? we cant get any help as we both work, on the other hand, his sons Mother that has never worked just like her lazy arse partner get rent, council tax, benfits and an extra wage doing fuck all!!

Apparently the only way to get it stopped for the mother to close the case which she is never going to do! any advice would be appreciated.