Sunderland have said they are "so very sorry" for letting down a 15-year-old fan who was groomed and sexually exploited by ex-player Adam Johnson.
It followed chief executive Margaret Byrne's resignation from the club after she admitted "a serious error of judgement" in advising the board that the winger could carry on playing after he was initially suspended last March.
Johnson, a Â£10 million signing, helped the Wearside team to narrowly avoid relegation from the Premier League last year under veteran Dutch boss Dick Advocaat.
Johnson was allowed to carry on playing until his trial at Bradford Crown Court where last month he stunned the club by admitting two charges of grooming the girl and kissing her.
He went on to be convicted of one further charge of sexual activity with a child.
During the trial, it emerged that on May 4, the chief executive met Johnson and Orlando Pownall QC, and she had social media messages exchanged and transcripts from police interviews in which the player admitted kissing the schoolgirl.
Pressure mounted on the club after the trial, with fans angry about what the club knew about Johnson, regardless of his stated intention to deny all charges.
Ms Byrne announced her resignation in a statement, and took full responsibility for what happened.
And the club responded saying Ms Byrne was "accountable for the actions taken by the club" and although she acted in Sunderland's best interest, investigations found decisions were taken "in error".
The club said: "Throughout this deeply regretful situation, we recognise that one devoted young fan and her family have been very badly let down, first and foremost by Mr Johnson and his despicable actions, but also by the club they support.
"We are so very sorry for this."
Leaving Sunderland after nine years, Ms Byrne said: "Contrary to what has been suggested, I did not understand that Mr Johnson intended to change his plea at trial or at all.
"I was astounded when he did plead guilty.
"I accept that Mr Johnson should not have been permitted to play again, irrespective of what he was going to plead.
"It was a serious error of judgment and I accept full responsibility for this."
She explained the decision to allow Johnson back into the squad last year came before he was charged.
Because he intended to deny all charges, he was "innocent until proven guilty", she said.
Ms Byrne also expressed sympathy to the girl who was groomed by the player she idolised.
She said: "Mr Johnson's victim has endured a terrible ordeal and for that I am truly sorry.
"At no time was the failure to suspend him again intended to cause any harm or distress to her or her family."
She said: "I recognise that, as CEO, my involvement with Mr Johnson and the decision to allow him to continue to represent the club was a serious mistake."
Ms Byrne, a lawyer, detailed how she put Johnson in touch with Mr Pownall after the player asked for advice about legal representation.
She said the player's father sent her some documents to be forwarded to the barrister, but she did not examine the contents of these documents "in any detail" and attended part of the introductory meeting with the eminent QC on May 4.
Mr Pownall sent her a note to forward to the player which said Johnson had kissed the victim and communicated with her.
She did not pass this information on to the board.
She added: "Mr Johnson remained innocent until proven guilty and I was concerned that any action taken by the club against him may be misinterpreted as a judgment on the club's part as to his guilt at a time when he steadfastly maintained his determination to plead not guilty and fight the charges.
"On that basis I recommended to the board that Mr Johnson should be allowed to play for the club, pending trial."