A four-week-old baby boy was attacked by a fox in his home in Bromley, the Metropolitan Police have said.
The boy was treated for a hand injury and taken to St Thomas' Hospital after the attack on 6 February, London Ambulance Service said.
London Mayor Boris Johnson said: "This sort of attack, though terrible, is rare, but we must do more to tackle the growing problem of urban foxes."
Police said their inquiries into the incident were continuing.
St Thomas' Hospital is not commenting on the incident.
Mr Johnson also said his thoughts were "with the baby boy and his family".
He added: "They may appear cuddly and romantic but foxes are also a pest and a menace, particularly in our cities.
"This must serve as a wake up call to London's borough leaders, who are responsible for pest control.
"They must come together, study the data, try to understand why this is becoming such a problem and act quickly to sort it out."
Mr Johnson has previously urged councils to take action over foxes following an attack in 2010 in which two baby sisters were mauled while sleeping at their home in Hackney, east London.
Both had to undergo surgery and were left scarred by the attack. Isabella Koupparis suffered arm injuries while her twin Lola suffered injuries to both her face and arm.
An RSPCA spokeswoman said it was extremely unusual for foxes to attack people and that the animal would only do so if it was afraid.
She added: "It's not typical fox behaviour at all. Foxes will come closer to a house if there are food sources. Then they can become quite bold, but they usually do back off and run away when there's people around."