Attempted murder charge after NSW bashing

A Sydney man has been charged with attempted murder after his partner was bashed so badly police had trouble determining her age.

The woman, believed to be 34, was attacked in a unit at Campsie about 5am on Thursday by a man wielding a knife and hammer.

Police said a 51-year-old in a relationship with her had been charged with attempted murder.

The woman was taken to St George hospital where she remains in a critical but stable condition.

The man has been refused bail and will appear in Burwood Local Court on Friday.

National domestic violence helpline: 1800 737 732 or 1800RESPECT. In an emergency call triple-zero.