A Wearside children's campaigner is calling for an investigation to be carried out into the way the Sunderland club handled the Adam Johnson situation.
Clare Phillipson, director of Wearside Women in Need, said fans feel betrayed by the club for continuing to allow Johnson to play despite the child abuse allegations.
And, she said despite a statement denying that the club knew he had groomed and kissed a 15-year-old girl, she believes more questions need to be answered as to why they allowed him to continue playing for the club, earning £3million before his trial.
In the statement issued last night the club insisted they had no knowledge Johnson was planning to plead guilty to those two charges at the start of the trial, and sacked him as soon as he did.
However, Ms Phillipson said the club still has a lot of questions to answer as to why they allowed him to keep playing for the club in the months leading up to the trial.
She said child protection experts should now carry out an inquiry at the club to find out exactly what bosses knew and did not know and to see if the club's child protection policy is up to scratch.
She said: "It is a catastrophic error of judgement that really has to have some fairly serious consequences for the club.
"In the North East we love our football and clubs are at the heart of their city.
"I know the fans I have spoken to feel betrayed. They don't appear to have considered the victim at all."
Ms Phillipson said of the club: "I think there are a lot of questions they have failed to answer and they have glossed over a lot of things.
"I am not saying they could have prevented it, because preditors are everywhere, they are very manipulative and can find their way into positions of power."
However, she said allowing Johnson to keep playing in matches gave the impression to the public that there were strong reasons to think the allegations were false.
She said: "What we need to know is, not at what point did they know he was going to plead guilty, but at what point did they know that he had met with her, exchanged messages and been alone with her in a car?"
The jury at Bradford Crown Court were initially told that the 28-year-old denied all the charges when he first appeared in court last May, meaning he carried on playing in the Premier League until early February.
He later changed his plea to guilty on two of the charges, and over the last two weeks, has been on trial for two others, being found guilty of one and not guilty of the other.
In a statement issued after the case, Sunderland AFC 'refuted' any suggestion the club knew all along that Johnson was intending to change his plea just before his trial so he could continue to play for them, and that the club may have been involved in tactical discussions about the plea.
It said: "Had the club known that Mr Johnson intended to plead guilty to any of these charges, then his employment would have been terminated immediately.
"On 23 April 2015, Mr Johnson was charged with four offences. The club was informed that it was Mr Johnson's intention to defend all the charges, a stance he maintained right up until the first day of trial. The club continued to review the safeguarding procedures it had put in place throughout this time."
They went on to add: "The club only became aware of the change of plea, in relation to two of the four counts on the indictment, on the first day of the trial, after hearing it reported through the media. The club was not advised in advance that Mr Johnson would plead guilty to any offence. Had the club known that Mr Johnson intended to plead guilty to any of these charges, then his employment would have been terminated immediately."