A mother in the United States tried to sew her adopted daughter’s mouth shut and forced her to eat dirty cat litter, police have said.

Rana Cooper, 46, was arrested earlier this week and has now been charged with assault and endangering children.

Police described Ms Cooper systematically abusing her adopted daughter, and said she had forced the 16-year-old to earn enough “points” by cleaning the house, which she could spend on the right to eat or use the toilet.

Local county children’s services had notified the police about the alleged abuse as early as May.

The girl told the authorities she was told she could only eat once a day, after the rest of the family had eaten.

“If it was time to eat and no one else was around, mother would allow child to eat and would make the child shovel food quickly into her mouth,” state police Cpl Robert Copechal wrote. “Mother would then make the child tell mother that she was eating one of her brothers.”

Allegations against Cooper also include choking her daughter until she blacked out, striking her face with a metal belt-buckle, and forcing her to scrape the inside of the toilet bowl with her finger and eat the resulting residue.

Police said Cooper had given them a written statement last month in which she admitted to holding her daughter's head underwater for as long as ten seconds.

Cooper's husband Richard is alleged to have witnessed some abuse by her. The 16-year-old girl was adopted by the couple in 2008 at the age of ten. They have six other children.

Cooper’s 24-year-old son Ronnie told local television station KDKA that none of the allegations were true. “Nothing. None of that happened,” he said.

The family live in Cross Creek Township, Pennsylvania, outside the major city of Pittsburgh.

The daughter has since been removed from the family home by children’s services and put in the care of an older brother and another carer.