FBI failed to investigate USA Gymnastics abuser, watchdog finds

The FBI disregarded allegations about a prolific USA Gymnastics child abuser and later made serious errors in the investigation, a watchdog has found.

The long-awaited report gave a scathing assessment of the FBI's investigation into former team doctor Larry Nassar.

He is serving an effective life sentence for molesting young gymnasts.

Numerous missteps and cover-ups by FBI agents allowed his abuse to continue for months after the case was first opened, the report found.

In a statement on Wednesday, the FBI acknowledged the findings, calling the handling of the Nassar file "inexcusable and a discredit to this organisation".

"We will take all necessary steps to ensure that the failures of the employees outlined in the report do not happen again," the agency said.