Scott Blackmun, the leader of the US Olympic Committee, has said he was not aware of the Larry Nassar sex abuse allegations before law enforcement got involved, and had no knowledge of a settlement between USA Gymnastics and McKayla Maroney in a case involving the now-imprisoned former team doctor.

Blackmun revealed this in a letter sent to key administrators and others in the US Olympic movement on Thursday, the day after Maroney filed a lawsuit seeking to invalidate the nondisclosure clauses in the settlement. Associated Press obtained a copy of the letter.

Along with USA Gymnastics and Michigan State University, where Nassar worked for decades, the USOC is named in the lawsuit, which it says had long promoted a culture that concealed known and suspected sex abusers.

In the letter, Blackmun said: “I am so sorry that the Olympic family failed these athletes,” and that while the USOC found out too late, it has taken steps to prevent future abuse by creating the US Center for SafeSport, which investigates sex-abuse allegations in Olympic sports.

“And I want to be crystal clear on the topic of transparency,” Blackmun wrote. “During my tenure as CEO, which began in 2010, we have never been, and will not be, party to any effort to conceal or keep confidential allegations or instances of sexual abuse.”

Maroney’s lawyer, John Manly, called the letter “repugnant”.

“If you’re the USOC and you’re really committed to this, what you should do is get on the phone to the USA [Gymnastics] board and say you’re out or we’re decertifying you,” Manly said.

He said Maroney’s main goal in the lawsuit is to be released from the nondisclosure and non-disparagement clauses in the settlement.

Maroney reached the settlement with USA Gymnastics in December 2016.

In October this year, she publicly revealed the extent of the abuse she suffered in a Twitter post, saying Nassar began abusing her when she was 13 and attending national team training camp.

Nassar has admitted to sexually assaulting female gymnasts, possessing child abuse images and molesting girls who sought treatment. He was sentenced earlier this month to serve 60 years in federal prison for possessing thousands of images of child abuse.