The man, 39, believed to be the children's father, will face no further action in relation to the deaths, police said.

He has been bailed to return to a police station at a later date in relation to another matter, details of which police would not release.

A six-month-old girl remains in a "critical but stable" condition after she was operated on by surgeons on Saturday night. Her five-year-old brother and a four-year-old sister died in hospital on Friday after being found injured at their home in Carshalton, south-east London.

A 35-year-old woman, believed to be the children's mother, remains under arrest in hospital, where she is being treated for minor injuries.

A spokesman for the Metropolitan Police said officers were called to the house at 10.30pm on Friday. "Police and London Ambulance attended and found three children suffering serious injuries, believed to be stab wounds," he said. "We believe we know the identity of the deceased. However, we await formal identification and confirmation that all family members have been informed."

Post-mortem examinations on the two victims are expected to be carried out early next week.

The two older children were taken to hospital but both died within 90 minutes of the police call. The girl died at 11.41pm and the boy 15 minutes later.

The £300,000 two-bedroom property in Park Lane was taped off as officers carried out an examination of the scene.

Neighbours said the couple were thought to be from the Tamil areas of Sri Lanka and had moved to the suburb in the last year.