The UK’s official Covid inquiry has no immediate plans to take further legal action against the Boris Johnson for failing to hand over his WhatsApp messages, openDemocracy understands.

Families of the bereaved say the inquiry “must be prepared to take legal action” against Johnson if his WhatsApps are not disclosed in their entirety.

Under Section 21 of the Inquiries Act, individuals must hand over any evidence demanded by the chair, with the failure to do so a criminal offence.

After the Cabinet Office launched and lost a judicial review – where it argued it could redact certain information it deemed “unambiguously irrelevant” from evidence – the government department has now handed over most of the material required under the Section 21 notice.

But Johnson’s old mobile phone, which was turned off in April 2021 due to a security breach, has not yet been handed over. It is understood the breach refers to the discovery at the end of April 2021 that the then-PM’s phone number had been freely available online for 15 years.

On Thursday, it was claimed his phone had not yet been handed to the inquiry because Johnson had forgotten the password – something experts have questioned. Previously, the Cabinet Office claimed that turning on the mobile phone could represent a security threat, which is why the messages had not been handed over.

It is understood the inquiry is not currently pursuing legal sanctions against Johnson as he is cooperating, and it believes no formal inquiry requirements or rules have been breached.

But Susie Flintham, spokesperson for Covid-19 Bereaved Families for Justice UK, said Johnson’s explanation as to why he had not passed on his messages was “a complete joke”.

“No one seriously believes that Johnson’s messages can’t be accessed because he forgot a passcode that he was apparently using last December,” said Flintham.

“Johnson needs to take full responsibility for ensuring that these messages are shared in their entirety with the inquiry, and the inquiry must be prepared to take legal action against him if he doesn’t.”

The inquiry said in a statement: “The inquiry has now received the materials required by the Section 21 notice issued to the Cabinet Office on 28 April 2023… [Johnson] is in possession of the ‘old phone’, is cooperating with the inquiry’s requests and efforts are underway to securely extract any potentially relevant content.”