A hospital chief executive told Lucy Letby “we’ve got your back” in an attempt to calm her father who was “threatening guns to my head” after she was stopped from caring for babies, a public inquiry has been told.

Tony Chambers said Letby’s father was “very upset and very angry” and wanted the “instant dismissal” of two senior doctors who had raised fears she was harming newborns.

Chambers told the Thirlwall inquiry he tried to “take the heat” out of the situation by telling the nurse she had been vindicated by several reviews and that she could return to the neonatal unit.

The inquiry heard that he told Letby at the end of one meeting in February 2017: “Lucy, don’t worry, we’ve got your back.”

Chambers admitted it was “clumsy language” and added: “As I’ve said all along, the intention here was to avoid any possible escalation and eight years on, with what we know … these are the kind of things you know you didn’t get right.”

Letby, now 34, is serving 15 whole-life prison terms after being convicted of murdering seven babies and attempting to murder another seven at the Countess of Chester hospital between June 2015 and June 2016.

The inquiry, led by Lady Justice Thirlwall, is examining the events surrounding the rise in deaths and collapses that year, which were first identified after three sudden and unexplained deaths in just 14 days in June 2015.

Chambers told the inquiry that Letby’s father, John, was “very upset and very angry” about how he felt the nurse had been treated by the hospital when she was removed from the neonatal unit in July 2016.

He said: “Letby’s father was very angry, he was making threats, he was making threats that would have just made an already difficult situation even worse by threatening GMC [General Medical Council] referrals, he’s threatening guns to my head and all sorts of things.”

The former hospital boss told Letby he would make several senior doctors apologise to her after she won an internal grievance process against her removal from the premature babies unit.

Nicholas de la Poer KC, counsel to the inquiry, suggested Letby was attempting to take control of the situation and being “deeply manipulative” in the knowledge she had murdered babies.

“I have to say I didn’t feel I was being manipulated at the time,” Chambers said. “It was her father that seemed to be pulling the strings as opposed to Letby herself.”

Chambers began his evidence by apologising to the victims’ families but he denied discouraging police from launching an investigation.

The former hospital boss said he “wholeheartedly accepted” that the Countess of Chester hospital’s “systems failed” and that there were missed opportunities to stop the nurse sooner.

He stopped short of identifying his own mistakes when asked six times to give examples of his personal failures.

Chambers said: “Right at the outset I’d just want to offer my heartfelt condolences to the families whose babies are at the heart of this inquiry. I can only imagine – well, I can’t imagine – the impact this has had on your lives and I am truly sorry for the pain that may have been prolonged by any decisions or actions that I took in good faith.

“I am very grateful to have this opportunity to take part openly and honestly in this inquiry and I hope the answers can be arrived at and recommendations made.”

Chambers, who said he was only made aware of the deaths on 29 June 2016, told the inquiry in his witness statement: “I wholeheartedly accept that the operation of the trust’s systems failed and there were opportunities missed to take earlier steps to identify what was happening.”

De la Poer said Chambers was not identifying any personal failure, prompting the former hospital boss to concede: “I take fully [sic] and accept that as the accountable officer for the trust I must take some responsibility for that, take responsibility for that.”

Chambers went on to deny that he discouraged the police from launching a criminal investigation when executives met senior officers in March 2017.

Minutes of the meeting show that the then chief executive told police there was “no evidence other than coincidence” and that executives believed the unexplained deaths and collapses were “certainly not criminal”.

“What we were saying is we can’t find any evidence of criminality – you’re the experts, please help us,” he said.

By the time of this meeting in May 2017, three external reviews had not ruled out deliberate or unintentional harm by Letby and several senior clinicians and the then deputy head of nursing, Sian Williams, were pushing for a police investigation.

De la Poer said Chambers failed to give the police a full account of the allegations against Letby that had been raised repeatedly by consultant paediatricians.

“I think that’s an unfair proposition,” Chambers replied. “We shared with the police very openly and candidly what we genuinely believed to be the position as we understood it at the time.”

The inquiry continues.