Parents of a 10-month-old boy who died from massive internal injuries on Christmas Eve have been warned that a jail term is "inevitable".
Neo Craig died from a punch to the stomach that caused fatal internal bleeding, the Old Bailey heard.
The baby lay dead for several hours before emergency crews were called to Rush Green Gardens in Romford, Essex.
Sharma Dookhooah, 25, and James Craig, 26, both drug users, admitted causing or allowing the death of a child.
Neighbours described the couple's stormy and violent relationship including the sound of plates being smashed, blows being exchanged, and swearing.
'Clenched fist'
Despite being on the "at risk" register, social workers failed to detect any bruising or injuries on a visit two months before Neo's death because he was covered in baby powder.
A post-mortem examination also showed that as well as his fatal injury he had suffered rib fractures and bruising and his head hair tested positive for cocaine.
Detective Chief Inspector Dave Marshall, who led the investigation, said: "Neo was subjected to inhumane and degrading treatment by the two people who should have cared for him.
"Today's guilty plea is a small consolation for Neo's grandparents who will not need to endure the further distress of a full trial."
Craig admitted lashing out with a "clenched fist" at his girlfriend while she was holding Neo during a row on 24 December 2006.
"Sharma Dookhooah moved slightly and the blow impacted on Neo," said Richard Whittam, prosecuting.
The case was adjourned until 8 November but Judge Richard Hone warned the couple that a jail term was "inevitable".
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