The British government on Thursday refused an order to hand over a sheaf of Boris Johnson’s personal messages to a Covid-19 pandemic inquiry that the former prime minister himself set up when he was the UK’s leader.

The head of the probe, retired judge Heather Hallett, asked to see notebooks, diaries and WhatsApp messages between Johnson and other officials that represent key evidence in the inquiry. The government provided incomplete versions, saying it cut personal and private information that was “unambiguously irrelevant” to the investigation.

Hallett, who has the power to summon evidence and question witnesses under oath, wants to judge for herself, and set a deadline of 4pm on Thursday for the government to hand over the unredacted documents, covering a two-year period from early 2020.

Soon after the deadline passed, the government said it would seek to challenge the order in court.

“The Cabinet Office has today sought leave to bring a judicial review” of the decision, it said. “We do so with regret.”

Just before the deadline expired, Prime Minister Rishi Sunak said his government would “comply, of course, with the law and cooperate with the inquiry”. “We are confident in our position but are carefully considering next steps,” he said.

WhatsApp is a favoured way for British politicians, officials and journalists to converse. The tone is often candid or casual, and potentially embarrassing. The government is worried about the precedent that disclosing Johnson’s full, unredacted conversations might set.

In a letter to the inquiry, the government’s Cabinet Office said there were “important issues of principle at stake here, affecting both the rights of individuals and the proper conduct of government”.

Boris Johnson admits he misled British MPs over lockdown parties

“Individuals, junior officials, current and former ministers and departments should not be required to provide material that is irrelevant to the inquiry’s work,” it said,

Hallett, however, has said that “the entire contents of the specified documents are of potential relevance to the lines of investigation being pursued by the inquiry”.

Rivka Gottlieb of Covid-19 Bereaved Families for Justice, a group that campaigned hard for a public inquiry, said it was “absolutely obscene that the Cabinet Office is going to spend hundreds of thousands of pounds of taxpayers’ money on suing its own public inquiry into being unable to access critical evidence”.

The issue has caused tension between Johnson and Sunak’s administration, which claimed this week that it did not have the material Hallett wanted. Both are Conservatives, but Sunak has tried to distance himself from the chaos that engulfed the government during Johnson’s scandal-plagued three-year term in office.

03:44

Boris Johnson apologises for attending ‘work’ party during Covid-19 lockdown

Boris Johnson apologises for attending ‘work’ party during Covid-19 lockdown

On Wednesday, Johnson’s office said the former prime minister had given the government all the material and urged authorities to give it to the inquiry. The Cabinet Office confirmed it had obtained Johnson’s notebooks and a trove of downloaded WhatsApp messages but said it had not received a response to a request for Johnson’s phone.

The UK has recorded more than 200,000 deaths among people testing positive for Covid-19, one of the highest tolls in Europe, and the decisions of Johnson’s government have been endlessly debated. Johnson agreed in late 2021 to hold an inquiry after pressure from bereaved families.

Hallett’s inquiry is due to investigate the UK’s preparedness for a pandemic, how the government responded and whether the “level of loss was inevitable or whether things could have been done better”.

Public hearings are expected to start June 13, and to last until 2026. UK public inquiries are often thorough, but rarely quick. An inquiry into the 2003 Iraq war and its aftermath began in 2009 and issued its 2.6-million-word report in 2016.

Ex-UK PM Johnson has earned US$1.2 million for speeches since quitting

Johnson is among the senior officials due to give evidence.

The inquiry has already landed Johnson in hot water. He was one of dozens of people fined last year for breaking his own government’s pandemic lockdown rules in the so-called Partygate scandal.

Last month, government-appointed lawyers helping Johnson prepare his submissions and testimony came across evidence of more potential breaches of Covid-19 restrictions. Civil servants reported the information to police, who say they are assessing the new evidence.

Johnson denies wrongdoing.