A married woman who leads a "staying out late" lifestyle involving "repeated nights drinking and clubbing" and "occasional casual sexual encounters" should no longer have day-to-day care of her toddler daughter, a family court judge has said.
Judge Sarah Singleton QC said the 23-year-old woman's way of life was "rather degraded and degrading" and "quite incompatible" with being a parent.
Social workers had raised concerns after a doctor concluded that "extensive bruising" on the girl - now aged 16 months - was consistent with "non-accidental injury".
They asked Judge Singleton to analyse the case and she concluded that either the woman - who is separated from the girl's father - or her partner caused the injuries.
She said it was "blindingly obvious" that the youngster should live with her father.
Detail of the case has emerged in a written ruling by the judge following at hearing at Blackburn County Court.
No one involved was identified but the judge said Lancashire County Council was the local authority with responsibility for the toddler's welfare.
Judge Singleton said the girl's parents separated shortly after she was born.
The father, who is in his early 30s, noticed bruising on his daughter's legs and an arm several months ago and she was taken into temporary foster care.
A doctor said the bruising was "extensive" and consistent with "non-accidental injury".
Social workers then asked the judge to decide how the girl was hurt.
Judge Singleton said she was "quite satisfied" that the injuries were caused by the mother or her partner, who is also in his early 30s.
The judge said the mother had been a "very poor witness" when giving evidence at the hearing.
"She did not appear to have any appreciation of why it is in (her daughter's) best interests and necessary for her future protection that there should be a proper investigation and consideration of what happened to her," said the judge.
"Her evidence also revealed that her lifestyle has become one of repeated nights drinking and clubbing and staying out late, with occasional casual sexual encounters. "
The judge added: "It is a rather degraded and degrading lifestyle, which puts her own safety at risk at the very least.
"It is also quite incompatible with being a parent, even when conducted on the nights when (the little girl) was not with her. If nothing else, it is likely to have caused her to be extremely tired. I cannot fathom why this mother allowed herself to sink to such levels of degraded and degrading conduct."
Judge Singleton went on: "The mother attributes the breakdown of her marriage to the fact that the father seemed to pay more attention and give more affection to (the little girl) than her. This seems to me to be a most unusual complaint by a new mother. The mother was thought by the father to be unhappy. He urged her to seek help."
The judge said she could not decide whether the mother or her boyfriend had injured the toddler but added: "I am quite satisfied that it was one of them. If it were not the mother, then she is responsible for a serious failure to protect."
She went on: "So far as the future is concerned, it now seems to me blindingly obvious that (the little girl) should live with her father."