Top US women gymnasts Simone Biles, Aly Raisman and McKayla Maroney at a Senate committee hearing on Wednesday, lambasted the FBI for covering up and delaying the investigation into sexual abuse that they suffered at the hands of disgraced former team doctor Larry Nassar.

The committee is examining shortcomings in the FBI's investigation into the Nassar case. He was later convicted of sexually abusing girls and is now serving a life sentence in jail.

"I blame Larry Nasser, and I also blame an entire system that enabled and perpetrated his abuse," BBC News quoted Simone Biles, the most decorated Olympic gymnast of all-time, as saying at the Senate hearing.

"If you allow a predator to harm children, the consequences will be swift and severe," she added.

Four-time Olympic gold medallist Simone Biles said the agents involved in the cover-up  should be prosecuted.

Aly Raisman, who was the captain of the 2012 and 2016 US Olympic gymnastics teams, criticised the FBI investigation as being "like guesswork." She said not addressing its serious flaws would result in a recurring nightmare for many more women.

McKayla Maroney, who won gold at the London 2012 Olympic Games, told the Senators that the FBI “chose to fabricate, to lie about what I said and protect a serial child molester."

"What is the point of reporting abuse if our own FBI agents are going to take it upon themselves to bury that report in a drawer?" she asked.

The three gymnasts were among more than 200 women who had testified in court in 2018, detailing Larry Nassar's abuse as the sports doctor of the United States women's national gymnastics team.

In total, Nassar was accused of sexual abuse by more than 330 women and girls at USA Gymnastics and Michigan State University.

A report into the FBI’s investigation had concluded that the FBI had been slow to respond and deliberate cover-ups by FBI agents had allowed Nassar's abuse to continue for several more months after investigations into the case had started.