Irishman critical after Sydney attack

An Irish tourist who suffered serious head injuries in an alleged one-punch attack by his brother remains in intensive care in a Sydney hospital.

Patrick Lyttle, 31, was allegedly punched during an argument with his brother Barry Lyttle, 33, on Bayswater Road, Potts Point, about 3am on Saturday.

Police say the younger man keeled backwards and hit the footpath when the punch was thrown.

Paramedics treated him at the scene before taking him to St Vincent's Hospital where he underwent emergency surgery.

His brother was charged with recklessly causing grievous bodily harm and was formally refused bail in court on Saturday.

A spokesman for St Vincent's Hospital told AAP on Sunday night that Patrick remained in intensive care in a critical but stable condition.

It's believed Barry and his father had flown in to visit Patrick, who arrived in Sydney for an all-round Australian trip last June.

Police have described the situation as a "family tragedy".