Nearly 100 witnesses are due to testify against the 54-year-old at a sentencing hearing, which entered a third day in Michigan today.

Nassar, who was jailed for 60 years in December for three counts relating to having child sex abuse images on his computer, has also admitted multiple sexual assault charges.

According to media reports, Judge Rosemarie Aquilina read aloud a six-page letter from Nassar today where he said he "feared for his mental health".

He also accused the judge of "grandstanding" and turning the court hearing into a "media circus" by making him listen to his victims.

"I have to say this isn't worth the paper it's written on," Aquilina said, as reported by The Guardian.

"You may find it harsh that you are here listening, but nothing is as harsh as what your victims endured for thousands of hours at your hands."

Aquilina added that the letter was "mumbo-jumbo".

"Spending four or five days listening to them is minor, considering the hours of pleasure you've had at their expense, ruining their lives," she said.

Four-time Olympic champion Simone Biles was this week the latest major American gymnast to allege she was sexually assaulted by Nassar.

Fellow Olympic gold medallists Gabby Douglas, Aly Raisman and McKayla Maroney have also spoken out against him.

Yesterday, Donna Markham said her daughter Chelsea had committed suicide following the abuse after first seeing Nassar for treatment aged ten.

In a statement read out by a prosecutor, Maroney said today that Nassar had "left scars on my psyche that may never go away".

It has been reported that Moroney would face a $100,000 (£72,000/€83,000) fine for speaking at the sentencing hearing because of a non-disclosure agreement.

Jamie Dantzscher, who won team Olympic bronze at Sydney 2000, also spoke today, telling Nassar he was "pure evil".

"I couldn't figure out what was wrong with me," she said, according to The Guardian. 

"Why I was struggling so much. 

"Why I didn't feel proud of my accomplishments. 

"I had zero self confidence."

Kerry Perry, the President and chief executive of USA Gymnastics who joined the governing body at the start of last month, has attended the sentencing hearing and has announced the body will no longer use the Karolyi Ranch training base in Huntsville where Nassar carried out abuse.

"I attended these proceedings to listen to the courageous women as they faced a despicable predator and explained in significant and painful detail the impact he had on each of their lives," she said. 

"Their powerful voices leave an indelible imprint on me and will impact my decisions as President and CEO every day. 

"I am profoundly saddened that a single woman was hurt. 

"As stated on my first day on December 1, 2017, I will not waiver on my commitment to remain focused each and every day on our organisation's highest priority - the safety, health and well-being of our athletes and creating a culture that empowers and supports them. 

"My commitment is uncompromising, and it is my hope that everything we do going forward makes this very clear."