A criminal probe into the hospital where Lucy Letby attacked babies has been widened to focus on individual staff, police have said.

Cheshire Police said it opened a corporate manslaughter investigation at the Countess of Chester Hospital in October 2023, focusing on the decisions of senior leaders.

However on Thursday the force said the scope of the investigation would now include potential offences of gross negligence manslaughter, which focused on the action or inaction of individuals.

Det Supt Paul Hughes said several suspects had been notified by the force but added that “no arrests or charges have yet been made”.

The senior investigating officer said: “This is a separate offence to corporate manslaughter and focuses on the grossly negligent action or inaction of individuals.

“It is important to note that this does not impact on the convictions of Lucy Letby for multiple offences of murder and attempted murder.”

Referring to the gross negligence manslaughter investigation, Det Supt Hughes said: “We will not be confirming the number of people involved or their identity.

“Both the corporate manslaughter and gross negligence manslaughter elements of the investigation are continuing and there are no set timescales for these.”

He also said his force was continuing to investigate the deaths and non-fatal collapses of babies at both the Countess of Chester Hospital and the Liverpool Women’s Hospital between 2012 and 2016.

“Our priority is to maintain the integrity of our ongoing investigations and to support the many families who are at the heart of these,” the senior detective said.

A spokesperson at the Countess of Chester Hospital NHS Foundation Trust said that due to ongoing police investigations it would not be appropriate for them to comment.

The news comes in the week before closing submissions are due to be delivered in the Thirlwall Inquiry at Liverpool Town Hall, a public inquiry examining events arounds Letby’s offending.

Barrister Mark McDonald, representing 35-year-old Letby, described the decision to widen the police investigation as a “huge mistake”.

Mr McDonald said: “We now have substantial and significant expert evidence which completely demolishes the prosecution case against Lucy Letby and points the finger in a very different direction to that which the police are currently looking.”

Last month, at a press conference arranged by Mr McDonald, an international panel of neonatologists and paediatric specialists claimed Letby was not responsible for attacking babies.

Panel chairman Dr Shoo Lee said “in all cases death or injury were due to natural causes or just bad medical care”.

The panel’s findings have been passed to the Criminal Cases Review Commission (CCRC), which investigates potential miscarriages of justice.

Letby’s legal team hopes her case will be referred back to the Court of Appeal which has the power to quash her conviction.

Letby, originally from Hereford, is serving 15 whole-life sentences after being convicted of murdering seven babies, and trying to kill seven others including one on two occasions, at the Countess of Chester Hospital’s neonatal unit between June 2015 and June 2016.

Thirlwall Inquiry chair Lady Justice Thirlwall is expected to publish her findings in the autumn.