Octomom -- Allegations of Sexual Abuse in the Home

7:00 AM PT -- Octomom has just responded to the allegations of sexual abuse -- telling TMZ, they are "BLATANT LIES" concocted by bitter ex-nannies.

Two of Octomom's former nannies have told officials ... Nadya Suleman allowed one of her children to sexually abuse another child inside the home ... this according to reports.

According to CBS2 in L.A., the 2 nannies have been in contact with Child Protective Services ... and told officials they personally witnessed the abuse.

The nannies do not say Octo personally sexually abused the children -- but according to one of the nannies who spoke with CBS, "(One of the boys) would take (his sibling) away and take her to another area. And he would be touching her."

"She never did (anything). ‘It’s okay, don’t worry about it.’ That was her attitude." the woman continued.

According to the report, the nannies also claim they witnessed Nadya tie her eight newborns to their bed with cheese cloths around their waists to keep them from getting out of their cribs ... and also blocked the door to the kids' bedroom with a chair from the outside so she could nap peacefully.

TMZ had obtained photos of a chair blocking the door several months back -- Octo said the kids had an exit and were never in danger.