The deadline for the UK government to hand over Boris Johnson’s WhatsApp messages, diaries and notebooks to the Covid-19 inquiry has been extended as officials claimed they did not have all the documents demanded.

The British Cabinet Office had been given until 4pm on Tuesday to comply with the order from Lady Hallett’s public inquiry, but that deadline has now been extended to the same time on Thursday.

Officials told her the Cabinet Office does not have the WhatsApp messages or notebooks called for by the inquiry.

A notice from the inquiry read: “First, an extension was requested for compliance with the ruling until Monday June 5 2023.

“Second, the inquiry was informed that the Cabinet Office does not have in its possession either Mr Johnson’s WhatsApp messages or Mr Johnson’s notebooks, as sought in the original section 21 Notice.

“The chair rejected the request for an extension of time to June 5 2023, but granted a short extension to 4pm on Thursday June 1 2023.”

British prime minister Rishi Sunak insisted the UK government was acting “in a spirit of transparency and candour”.

“The Government has co-operated with the inquiry; tens of thousands of documents have been handed over.

“With regard to the specific question at the moment, the Government is carefully considering its position, but it is confident in the approach that it’s taking.”