Los Angeles, Nov 6 (IANS): Actress Denise Richards has refused to take care of her ex-husband Charlie Sheen's four-year-old twins claiming they are violent towards her daughters and dogs.

The 42-year-old was granted temporary custody of Sheen and Brooke Mueller's sons - Bob and Max - in May until the end of this year after their mother's drug use spiralled out of control.

The actress, who has two daughters - Sam, nine and Lola, eight with Sheen - as well as two-year-old adopted daughter Eloise, wrote a distressing letter to the Los Angeles County Department of Children and Family Services (DCFS), blaming Mueller for her sons' bad behaviour.

A source told tmz.com that Richards said the boys often go into a "zombie-like state" and gave details about their violent behaviour, including one incident that saw Bob throw a toy at Sam's face forcing Richards to take her to the doctor.

The former "Bond" girl also claimed that Bob and Max have even harmed other children and slapped their teachers in school.

Richards' damaging letter backs up Sheen's claims that his sons act out after spending time with their mother.

Brooke and the "Anger Management" star have been in a bitter custody battle since her release from rehab with Sheen branding her as an "evil and pathetic uber loser" in a rant about her on Twitter last week.

She is now preparing to go to court about his comments as everyone involved in the custody and guardianship cases have been ordered not to discuss the situation.