Video report by ITV News Correspondent Juliet Bremner
The mother of a 14-year-old girl who died under the care of The Priory says a £300,000 fine for the firm shows the firm put "profit before safety".
Tania El-Keria said the fine following her daughter Tania's death had opened the public's eyes for what the Priory stood for - and hailed an "historic day for justice".
She said: "Our Amy died in what we know to be a criminally unsafe hospital being run by the Priory.
"To us, the Priory are a morally-bankrupt company.
"They continue to take large sums of public money allowing our children to suffer by placing profit over safety."
Amy was found in her room at Ticehurst House in East Sussex in November 2012 while receiving treatment at the Priory, a private firm which runs mental health services as part of a contract with the NHS.
A jury inquest in 2016 heard neglect contributed to her death and found she died accidentally of unintended consequences of a deliberate act.
The Health and Safety Executive (HSE) pursued a criminal investigation and the company admitted to a charge of being an employer failing to discharge its duty to ensure people were not exposed to health and safety risks.
Speaking on Wednesday outside Lewes Crown Court, Ms El-Keria said: "It's not about the fine, it's not about the money."
She said the Priory's contract with the NHS should be ended.
"I don't believe there's any lessons learned," she added.
Sentencing, Judge Mr Justice James Dingemans had earlier said that following work between the Priory and the Care Quality Commission there was now a much better understanding of young person suicide, and that "vital lessons have been learned".
But, today Mr Justice Dingemans said he was "unable to be sure... that the offence was a cause of Amy's death".
He concluded that there was a "low likelihood" of harm in the case but culpability should be assessed as "high" as patients including Amy were exposed to risks to their health and safety.
"They only took action after her death. Further, Priory Healthcare failed to make appropriate changes when required to do so by the CQC," he said.
"There was, in my judgment, insufficient urgency demonstrated in dealing with these problems."
At an earlier hearing, Prosecutor Sarah Le Fevre had said the starting point for the fine would be £2.4 million.
Mr Justice Dingemans said Priory Healthcare had a turnover of £133 million in 2017, with an operating profit of £2 million that year.
He said he was unable to find any aggravating factors and he took into account the company's guilty plea, lack of previous convictions, "good" health and safety record and its steps to close and refurbish the unit where Amy lived.
In a statement, Priory Group CEO Trevor Torrington offered "sincere and profound apologies to Amy's family".
Mr Torrington added: "There was common ground between the experts that the care planning was of good quality, that the suicide of 14-year-olds is extremely rare and prediction is likely to be extremely difficult."
He said they accepted some risk management procedures and training were not robust enough.
"However, the court found such shortcomings were not causative of Amy's tragic death," he added.
At the earlier hearing, the court was told that Amy had arrived at the hospital's high dependency unit on August 23 2012.
On November 12, at 8.15pm, she was found in her bedroom with a ligature tied around her neck and taken to Conquest Hospital in Hastings, where she died the following day after life support was withdrawn.
Ms Le Fevre told the court that information relating to Amy's care had not been properly handled.
A ligature audit of her room, carried out by an untrained member of staff, identified medium risks which were not followed up.
The hospital was also slow to tackle concerns over risks identified in a CQC inspection in November 2011.
Details of a conversation on suicide Amy had with a nurse in the early hours of November 12 were not passed on to her doctor.
The 2016 inquest jury's findings were highly critical of the Priory, ruling staff failed to dial 999 quickly enough, failed to call a doctor promptly and were not trained in CPR.
The response of staff was so inadequate the jury agreed there was a possibility that Amy may have lived if she had received proper care.