Police have revealed a letter to 2GB – supposedly detailing a hit-run accident, which has left an eight year old Sydney girl in a critical condition – is nothing more than a cruel hoax.

The letter, also sent to The Daily Telegraph, contained registration details of the car allegedly involved and another at the scene. Georgina Woods has brain damage and has been in a medically induced coma since Monday with head injuries, compound fractures and bleeding lungs.

2GB and the Telegraph released copies of the typed letter, in which the author said he wanted to remain anonymous.

“(I) hope you will understand that we want to remain anonymous as my family members want it that way.

“… When this driver is arrested, we will get in touch with you personally.”

The man claimed he saw the accident and called Crime Stoppers minutes later, but the operator reportedly hung up after the caller failed to disclose his identity.

In the letter, ‘Steve’ says: “The dark coloured car that hit the girl was driven by an ***** driver. Numberplate ****** (not revealed for legal reasons).

“A red car following behind closely with driver and passenger, both non-*****, bearing numberplate ****** shouted at the ***** fellow: ‘Go, go, go, don’t stop’.

“Obviously, both drivers of these cars must be knowing each other . They both took off at high speed.”

Police have ruled out both vehicles in their investigation, and say they intend to find and charge the author of the letter.