The Cabinet Office was on Wednesday accused of holding back evidence relating to Boris Johnson's handling of the Covid pandemic.
The official UK Covid Inquiry threatened legal action over the refusal to supply the then-Prime Minister's unedited WhatsApp messages with dozens of Government figures, including Rishi Sunak, and 24 notebooks.
Baroness Heather Hallett, who is leading the probe, said the content should not have been redacted before it was handed to her team.
She issued a Section 21 notices on April 28, demanding the full documents.
In a letter to the Cabinet Office, she warned that the Government is “required to supply these materials to the UK Covid-19 Inquiry by the dates set out”.
“Failure to comply with this Notice without reasonable excuse is a criminal offence, punishable on summary conviction with a fine not exceeding £1,000 and/or imprisonment for a maximum of 51 weeks.”
The Cabinet Office argued that the materials requested were “sensitive” and the inquiry had “no entitlement” to them.
“The more senior the Government Minister, official or advisor targeted by the Inquiry’s disclosure requests, the more likely it is that their communications will address, in particular, policy matters of particular sensitivity which are unambiguously irrelevant to Covid-19 and which should not be disclosed outside of Government without it being strictly necessary to do so,” the Cabinet Office said in its reply.
But Baroness Hallett said it was for the public inquiry to decide what was relevant.
She asked for unredacted WhatsApp messages from Mr Johnson and a senior Number 10 advisor between January 1, 2020 and February 24, 2022. Unredacted diaries for the former Prime Minister covering the same period were also requested.
It comes as Mr Johnson was referred to the police by the Cabinet Office over fresh claims he broke lockdown rules.
The Uxbridge and South Ruislip MP has severed ties with his Government-appointed lawyers and is now seeking new legal representation.
In a letter to Baroness Hallett, Mr Johnson said the process “is well underway but is in the hands of the Cabinet Office to agree funding and other practical arrangements”.
“I have no control over the timing of that process,” he said. “I am unrepresented and my counsel team have been instructed not to provide me with any advice.
In regard to the Section 21 Notice, he told the Covid Inquiry chairwoman: “I have never seen the Notice, I was not party to nor have seen the Cabinet Office’s representations under s21(4), and I am not allowed to see your ruling before it is published.
“This is highly prejudicial to me given that I believe your ruling may directly and/or indirectly suggest that I have failed to provide documents to the Inquiry.
“Any such suggestion or implication would be unfair and untrue. The Notice was issued before the deadline had passed for me to provide material to the Inquiry. I have always sought to comply with all disclosure requests from the Inquiry and I have already disclosed over 5,000 pages of documents and over 300 pages of emails.”
More than 55,000 documents and 24 personal witness statements have also already been sent to investigators.
Downing Street said it has no duty to disclose “unambiguously irrelevant” material.