Father assaulted four-week-old: NSW Police

A four-week-old baby girl has been left with critical head and chest injuries after allegedly being assaulted by her father in Sydney's south west.

Police on Tuesday arrested the 25-year-old man, less than a week after the newborn was taken to hospital suffering seizures.

Doctors found she had suffered serious brain, neck and rib injuries, and detectives from the child abuse squad were notified.

The man was charged with recklessly inflicting grievous bodily harm.

He was refused bail to appear before Parramatta Local Court on Wednesday.

The child remains in a critical but stable condition at Westmead Children's Hospital.