Woman who allegedly stabbed partner 'only intended to poke him'

A 37-year-old man is in a critical condition after a stabbing at a home in Sydney's west.

Police were called to a South Penrith address just before 3pm yesterday where they found Mark Hopkins with a serious stab wound to his chest.

He was taken to Westmead Hospital in a critical condition and underwent surgery overnight.

Mr Hopkins 19-year-old partner Tara Kruse was arrested, charged and refused bail.

"He was gasping and there was a lot of blood it was a bit shocking and a little bit scary," neighbour Scott McGillycuddy told 9NEWS. 

Ms Kruse faced court today charged with causing grievous bodily harm with intent and breaching an apprehended domestic violence order taken out against her.

Police facts allege she claims she had only intended to poke him.

The 19-year-old's application for bail was formally refused today.

The court heard she could pose as an unacceptable risk to her alleged victim.

Ms Kruse will appear again in court again next month.