A 24-year-old man was stabbed five times as he tried to fend off armed gatecrashers at his teenage niece's birthday party in South Croydon.
Teenagers armed with knives and bats are thought to have tried to force their way into the girl’s 14th birthday party at house in Nottingham Road on Saturday night.
The victim is in hospital with serious injuries after being stabbed repeatedly.
The party was for 30 guests and was intended to last from 6pm to 9pm, according to relatives.
But towards the end of the evening a large groups of teenagers were said to have showed up armed with knives and bats and attempted to force their way into the house.
Peter Holness, the victim’s brother, said: "Some of the uninvited children got rowdy and started to push and shove the way through the door making a noise [and] acting in a disrespectful manner.
"A gang of kids rushed through the door and [stabbed] my brother five times. He is in critical condition at St George’s Hospital [and] his condition is still unstable."
Mr Holness said he believed the gatecrashing teenagers were aged between 12 and 17 and attended two Croydon secondary schools.
Vesko Kichukov, 30, who lives next door to the house where the stabbing happened, said he knew there had been a party on Saturday night but had not heard about the attack.
He said: "I saw police coming and an ambulance about 9.30-10pm, but I thought that was normal - nothing unusual for a party."
A Metropolitan Police spokeswoman said officers were called to a house in Nottingham Road just before 9.30pm on Saturday night.