The couple, who have two children together aged 4 and 3, split up early last year. They recently came to a custody agreement whereby the children's "main home" would be with their mother.
According to The People, Croft will pay £1.66 a week for each child with Katona, and for the child he fathered before marrying the ex-Atomic Kitten singer. The unidentified woman with whom Croft has his first child is said to be "disgusted" at the Child Support Agency's decision.
"The mum is disgusted," said a friend of the woman. "She found out Mark was the father of her son in 2008 through a DNA test. It was even screened on Kerry's MTV show, with Mark publicly washing his hands of the child.
"She wanted to reach an amicable agreement for maintenance but Mark refused to pay a penny, even though he was, at that point, being paid 20% of Kerry's earnings.
"The mum had no choice but to go to the CSA. She didn't think it was fair for Mark to be parading his wealth on TV while she struggled to bring up their son. This nightmare has been going on for years.
"It's sickening that he's driving round in a sports car and only paying a fiver a week for three kids.
"That doesn't even pay for one school dinner for his child from before he met Kerry and it won't even go near the private school fees Kerry pays for her kids.
"But the CSA seems to be happy to let him get away with it. He is laughing all the way to the bank."