Sydney teen critical as party gatecrashed (AAP)

View CommentsAAP A teen is in a critical condition in hospital after being stabbed at a party in Sydney's inner west.

It was meant to be a small gathering of friends for a 14-year-old girl's birthday.

But the get-together at a house in Five Dock, in Sydney's inner west, turned into a violent brawl after gatecrashers showed up.

Now a teenage boy is fighting for his life in hospital after being stabbed several times at the out-of-control party on Friday night.

Another is facing criminal charges.

Police were called to the home on Charles Street and found two injured teenagers in the backyard.

A 17-year-old boy was stabbed in the chest and in his side and is in hospital in a critical but stable condition.

On Saturday a 16-year-old, who also sustained minor head injuries during the brawl, was charged with assault and affray. He was released on bail and is expected to appear at a children's court on June 20.

Another teenager, 17, was allegedly hit in the head with a bottle and was also taken to hospital. He was discharged on Saturday.

It is understood a 14-year-old girl, who was staying at the dual-level brick home with her grandparents, was having friends over for her birthday.

Her grandmother told AAP she allowed the girl to have half a dozen people over but the gathering was gatecrashed.

She said she was coming home from the Blue Mountains when she received a call from her daughter telling her the party had escalated.

"I went straight to Burwood police station," she said on Saturday morning.

It is understood most of the party-goers were from Concord High School.

The granddaughter is now with her father and on her way to Canberra, the woman, who did not want to be named, said.

Burwood police Inspector Michael Penfold said officers faced chaotic scenes when they arrived on Friday night.

He said there was at least one adult home.

Surrounding residents of the usually quiet suburban street heard bottles smashing and people screaming.

Jay Nam looked out her window to see young people on the street yelling at each other.

"Some of the residents came out and tried to get them away from the street," she said.

Next-door neighbour Ed White said the party-goers were about 15 or 16 years old.

"They were really young," he said.

"There was just lights flashing, sirens and cops up and down the street."

Insp Penfold had a warning for parents planning a party for their children.

"One of the main issues is make sure only invited guests attend and adequate security provisions beforehand," he said.

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