A mother has said she faced a police investigation after her newborn baby suffered a heart attack that, it was later concluded, was probably caused by excessive magnesium in a hospital feed.
Frances Blacklock's son Mason was born by Caesarean section in February 2012 and needed surgery to reposition his bowel and correct a birth defect.
After the operation, he was transferred back to University College London Hospital, where he was born, and began to breathe on his own.
But Ms Blacklock said she received a call saying his condition had worsened.
" I was told to come to the hospital as soon as possible, as Mason was back on an incubator," she said. "When I got there, he was also on a ventilator and looked grey. It was horrific but no one could tell what had happened."
Lawyers from Irwin Mitchell, which is acting for the mother of two from Barnet, north London, claimed she was told Mason had suffered a cardiac arrest, and also that police would be investigating, amid concerns that he could have been poisoned.
A year-long investigation by the hospital, Metropolitan Police and the Medicines and Healthcare Products Regulatory Agency (MHRA) eventually concluded that the illness was caused by excessive magnesium found in the intravenous feed given to the baby, according to the law firm.
Ms Blacklock has now instructed lawyers to obtain redress from the manufacturer of the feed.
She said: " The investigation was awful, even my partner and I had to be eliminated from suspicion. To be involved in something like that was just heartbreaking, especially when all we cared about was Mason getting better."
Mason survived and is now two and a half, and his mother said she hopes he is on his way to a full recovery.
Ms Blacklock and her legal team called for a review of safety regulations after recent, separate, cases which saw several babies struck down with blood poisoning from a suspected contaminated drip.
She said: "We want to know how these problems happened and what is being done to prevent them from happening again. No one else should have to face what we have been through and lessons must be learned."
David Body, a partner at Irwin Mitchell who is representing the mother and her son, said the recent reports had "shone a spotlight on this issue".
He said: "Understandably, parents also expect that the safety of the medical products with which their children are treated in hospital will be of the highest standard, which is why it is vital that the MHRA takes steps to regulate these products as closely as possible in future and ensure that the highest safety standards are upheld - parents of children in neonatal intensive care need that reassurance."
An MHRA spokesman said it takes such incidents "very seriously" and confirmed it carried out an investigation with police.
He said: " The investigation concluded that the most likely cause of this incident was a manufacturing error that saw excessive magnesium included in the product. We oversaw the implementation of a thorough corrective action plan by the manufacturer to minimise the risk of this happening again."
A Scotland Yard spokesman said specialist detectives investigated the circumstances of an incident involving "abnormal readings" taken from the baby's blood samples.
He added that the investigation concluded last year that there had been no criminal offence, no one was arrested and no further action was taken.
The manufacturer of the feed was not available for comment.
A hospital spokesman said: "Mason came to us as a very sick baby and when he was six days old his condition deteriorated rapidly.
"Due to the astute intervention of our clinical team, this was found to be due to high levels of magnesium in Mason's blood.
"We are pleased that our swift intervention saved his life. We are in regular contact with Mason's family - who have nothing but praise for our care - and are delighted that he has grown into a healthy two-year-old.
"We worked closely with the police throughout this incident and there was absolutely no evidence of any wrongdoing by UCLH or our staff."