Letby interviewed in prison over more baby deaths

Barrister Mark McDonald added: "The police have been briefing about further enquiries for over a year.

"Any allegations need to be taken seriously so we are only surprised by the timing of this new leak from the police."

The police statement confirming Letby had been quizzed over more baby deaths followed reporting in the Daily Mail.

The force said more information would be released "at the appropriate time".

Letby is serving 15 whole-life orders for murdering seven babies and attempting to murder seven other infants between June 2015 and June 2016.

Letby, originally from Hereford, made two attempts to kill one of her victims.

Following her convictions, Cheshire Constabulary revealed officers were investigating the time she had spent on two placements at Liverpool Women's Hospital.

It is part of a wider examination into Letby's whole career.

This involves reviewing more than 4,000 admissions into neonatal units where Letby had been present.

Letby's crimes and the implications for the NHS are currently being examined at the Thirlwall Inquiry.

The lead paediatric consultant at the Countess of Chester, who originally raised the alarm about Letby, testified last month.

Dr Stephen Brearey told the inquiry at Liverpool Town Hall: "On reflection I think it's likely that Letby didn’t start [to] become a killer in June 2015, or didn’t start harming babies in 2015."

In September, a barrister representing the families of 12 babies said Liverpool Women's Hospital had conducted its own audit into Letby's time there.

Richard Baker KC told the inquiry that babies' breathing tubes were dislodged at an "unusual" rate while she was on shift.

The inquiry heard they became dislodged in about 40% of her shifts, compared to this "occurring generally in less than 1% of shifts".

However, there has also been significant debate over the science used in the case against Letby.

A number of experts have challenged the medical evidence used to convict her.

Letby's new legal team also take a different view of the new evidence.

They have said they plan to take her case to the Criminal Cases Review Commission next year, to apply for it to be sent back to the Court of Appeal.

On the recent police interview, Mr McDonald said: "Lucy voluntarily attended an interview; she was not arrested.

"Lucy continues to maintain her innocence and as she has said throughout she has never and would never harm any child."

Letby has twice been denied permission to appeal against her convictions.

The Thirlwall Inquiry has also heard from the Countess of Chester's bosses in recent days, some of whom are speaking publicly about the case for the first time.

Former chairman Sir Duncan Nichol told the inquiry that his decision to not invite the doctors who suspected her to an important meeting was "a big personal failure".