An allegation that a young boy was abducted in south London was invented by a nine-year-old boy.
Police began investigating the claim after two genuine incidents in which the abduction of young girls was attempted in Croydon.
But the most recent allegation, made by a boy who claimed to have seen a youngster being taken, was taken back.
A Met spokesman said: "The allegation has been withdrawn. We are satisfied it could not have taken place."
The force had been told a dark four-wheel drive car pulled over and a white boy aged about 10 was taken.
One parent told BBC London: "Rumours were rife in the school playground that it may have been a hoax, as no child has apparently been reported missing by anyone."
Because of the age of the boy, a charge of wasting police time will not be considered.
On 28 May police warned south London parents to be on guard after two apparent abduction attempts.
The first girl, aged 11, was grabbed by a man driving a white car on 10 May in Croydon but escaped.
Then a 14-year-old girl wriggled free from the grasp of a man, again driving a white car.
The parent said about the abductions attempts: "Croydon parents are very scared at the moment. I have two girls and I for one certainly wont be letting them out of my sight."
Police put extra patrols on in the area and appealed for the public to remain vigilant.