The “serious concern raised” about a rise in infant deaths at the Countess of Chester Hospital should be shared openly at a public inquiry into Lucy Letby’s crimes, an inspection chief has said.

An inspection team from the Care Quality Commission (CQC) was not informed when they visited the hospital in mid-February 2016 that there had been a sudden increase in neonatal deaths or that some deaths were unexpected and unexplained.

The killer nurse had already killed five babies by then, and attempted to kill a girl named Child K by removing her breathing tube during an examination in the early morning hours of February 17.

A week before the inspection, an external “thematic” review of 10 deaths on the unit in 2015 and January 2016 noted that “some of the infants had deteriorated suddenly and unexpectedly and there was no clear cause for deterioration/death identified”.

It also found that six babies had been arrested between midnight and 4am, but concluded that there was no common theme across all cases examined.

Medical director Ian Harvey and nursing manager Alison Kelly received copies of the review the day before the inspection after Mr Harvey requested the CQC visit, the Thirlwall Inquiry heard.

But investigators from the health services regulator told the inquiry they were not told about the review when they were interviewed on-site.

Giving evidence on Friday, CQC’s regional head of hospital inspections, Ann Ford, said: “This was different.

“This wasn’t just information.

“This was about a serious concern that was raised.

“This was a really important issue and I think they should have informed us immediately.

“Every document, every audit, every review, every study they did had to be shared transparently and openly.

“I really think the trust has a professional obligation and an obligation to patients to be open and transparent with us, and I would have liked to have known about those concerns sooner.”

He said he first learned of the increase in neonatal deaths in a phone call from Ms Kelly on June 29, 2016, when the inspection report was published earlier that day and rated services for children and young people as “good”.

Ms Kelly said a number of measures had been taken, including reducing the quality of the neonatal unit and moving babies in intensive care to other centres, but Letby was not mentioned, Ms Ford said.

Ms Ford told the hearing: “I think we need to be alerted to a practitioner’s concerns in the unit and how they manage it.”

The inspection chief also said concerns were raised by consultants during the inspection that they were being “pressured” and “bullied” by senior management.

He said the comments were made during a focus group meeting and also included concerns about staffing levels and the trust not listening to them.

Ms Ford said she thought the feedback was later raised with Mr Harvey by investigators.

He said: “His reaction, as I understand it, was that they were working on the culture of the trust and that the consultant would speak to the organization and begin to address those concerns.”

Letby, 34, from Hereford, is serving 15 life sentences after being found guilty at Manchester Crown Court of murdering seven babies and attempting to murder seven more between June 2015 and June 2016, as well as making two attempts on one of his victims.

The investigation at Liverpool City Hall is expected to run until early 2025, with findings published in the late autumn of that year.