The mother of one of Valdo Calocane’s victims says she has “lost faith” in Nottinghamshire Police’s leadership and called for the chief constable to step aside while allegations of failings are investigated.

Emma Webber raised concerns after it emerged the son of the force’s boss Kate Meynell was among members of a police WhatsApp group in which graphic details were posted about the killings in Nottingham last year.

The force is being investigated by both the police watchdog the Independent Office of Police Conduct (IOPC) and the College of Policing after coming under fire over its handling of the case.

Mrs Webber, whose 19-year-old son Barnaby was among those killed, told the PA news agency: “Kate Meynell has told us her communication with the families has been, and will be, transparent and open.

“Sadly, this is very far from the case, and as such we have lost faith and respect for Nottinghamshire Police leadership.

“We have had in writing that no further answers to our questions will be forthcoming and, therefore, we agree that it may be preferable that during the investigations of the IOPC and College of Policing she steps aside, certainly for interactions with the families of the Nottingham attacks.”

Mrs Webber said the families had concerns about the personal conduct of the chief constable and her judgment in the matter, as well as those of assistant chief constable Rob Griffin and the senior investigating officer in the case, Leigh Sanders.

The families believe there have been “grievous failings in both the management of this investigation and also in alarming failures and missed opportunities in previous contact with Calocane”, she said.

“We wish to ensure a thorough investigation takes place on all aspects of these areas. And if our fears are founded then it must be the case that full individual and organisational accountability happens as a result,” Mrs Webber added.

The force said it was unable to comment while the probes continued.

The IOPC is still in the process of outlining the scope of its investigation so it is not yet known whether Ms Meynell’s conduct will be considered as part of the probe.

“We will be speaking with the families soon about their allegations before we finalise the terms of reference for our inquiries,” an IOPC spokesman said.

Earlier this week the families said they “will not be silenced” and accused the force of trying to “gag” the press in a bid to stop details of failings being made public.

A force investigation found 11 members of staff viewed material about the case without any legitimate reason for doing so. Three faced disciplinary action but eight were instead handed “performance interventions”.

Last week, Ms Meynell said she was “horrified” after one of her officers viewed bodycam footage showing the aftermath of the attacks. The special constable was sacked in December.

Meanwhile, police constable Matthew Gell was given a final written warning after a misconduct hearing in January found he breached confidentiality standards after sharing information about the case in a text message.

Another staff member is also due to face misconduct proceedings.

In a statement the families described the language used by Pc Gell in the WhatsApp group as “abhorrent and unforgivable”.

They said they were told that the “son of the chief constable was in the WhatsApp group although he had not been found to have partaken in the discussion” and accused Ms Meynell of later refusing to answer further questions about the WhatsApp group.

The chief constable also “denied” Mrs Webber the chance to tell the officers involved in the group “how the unprofessional and cruel language used has hurt the families even more”, the statement claimed.

Asked if he was concerned about the force’s conduct, after the families wrote to him about the case, Home Secretary James Cleverly told PA he supported the IOPC investigation and the “formal assessment” of the force’s performance should take place “without my comments or intervention”.

“I’ve met the families, I know how strongly they feel about this. I know that they are very dignified in their response to these tragic circumstances. But I want to let the IOPC do its work,” he said during a trip to the US.

Last week, Ms Meynell insisted the force had taken disciplinary matters “extremely seriously”, adding: “There’s lots of things I can’t say. And that’s not because I don’t want to, it’s because there’s the ongoing reviews into what happened.”

Nottinghamshire Police said: “The family have raised a number of concerns and the appropriate way for these to be resolved is through the ongoing independent investigation by the IOPC as well as the review by the College of Policing.

“Commenting further could prejudice these investigations.

“We have written to the families of all of those affected by this horrific crime and offered to meet them.”

Calocane was sentenced to an indefinite hospital order last month for stabbing to death university students Mr Webber and Grace O’Malley-Kumar, 19, as well as school caretaker Ian Coates, 65, in the early hours of June 13 last year.

He admitted manslaughter by diminished responsibility and pleaded guilty to the attempted murder of three people who were hit by a van stolen from Mr Coates, after Nottingham Crown Court heard he had been diagnosed with paranoid schizophrenia.

Prosecutors decided not to pursue murder charges, prompting an outcry of anger from his victims’ relatives.

Attorney General Victoria Prentis has confirmed she will ask the Court of Appeal to review the sentence.

A series of other investigations into the actions of prosecutors and mental health staff also continues.

The Government previously said it had not ruled out launching a public inquiry to consider claims of missed opportunities to stop Calocane before the killings amid calls for a wider investigation, but so far one has not been announced.