The mother of a baby girl murdered by Lucy Letby has demanded an apology from the hospital for “dozens” of failings that allowed her daughter to be “preyed on” by the nurse.

The Thirlwall inquiry was told on Tuesday that Child D, a premature newborn girl, was in a good condition before she was attacked three times by Letby overnight at the Countess of Chester hospital in 2015.

Letby, 34, is serving a whole life prison term after being convicted of murdering Child D and six other babies, and attempting to kill seven others, following two trials at Manchester crown court.

The mother of Child D told the inquiry into the killings that her life “crumbled” when her two-day-old daughter died on the hospital’s neonatal unit in the early hours of 22 June 2015.

Giving evidence on Tuesday, she described how she felt she was “losing my mind” as she demanded the medical notes and pushed for investigations into her daughter’s death.

“My husband was extremely worried because I was asking too many questions and requesting notes and I was investigating and going to the police and I felt I was losing my mind,” she told the inquiry chair, Lady Justice Thirlwall.

Months after Child D’s death, the witness said, a review concluded she should have been provided with antibiotics earlier but that this might not have changed the outcome for her daughter. A postmortem examination had attributed the newborn’s death to acute pneumonia.

Child D’s mother said she kept pushing for answers, including writing to the coroner to request a full inquest into her daughter’s death, because “it just didn’t match up”.

She said she felt “dismissed” and “very upset” after being fed “rubbish” by the hospital and its medical director, Ian Harvey.

She accused Harvey of “lying” to the public when he claimed in a BBC News article in February 2017 that investigations had concluded into the increased rate of neonatal deaths and that families could now be fully informed. She said that even three months later she was “getting nothing, no answers”.

It was only on the morning that Letby was arrested, in July 2018, that she learned of any police involvement, she told the inquiry.

She added: “We had to piece the whole picture together pretty much during the trial. That’s when we were finding out information and that’s when things started to make sense.

“But to me if I wasn’t failed in the first place by the Countess in dozens of ways – and all against the protocol and guidelines they should have followed – my daughter wouldn’t have ended up in intensive care, I wouldn’t end up poorly and destroyed, and she wouldn’t end up in a place where someone is preying on babies.”

She said the Countess of Chester hospital NHS Foundation Trust should apologise to “all the families who have suffered”.

The Countess of Chester hospital said in its opening statement that it was “profoundly sorry” for the families’ suffering.

Harvey and other senior managers have said they were “deeply sorry” for failures in communicating with the bereaved parents. “In hindsight, we should have communicated far better than we did,” they said in a written statement published last week.

Child D’s mother said she “felt very uneasy” in Letby’s presence before her daughter became seriously unwell, recalling how she told her husband she felt “uncomfortable” with the nurse “just watching” with apparently no other reason to be in the room.

“With the benefit of hindsight and what I know now [and] I had what some would call instinct, I felt very uneasy in her presence.”