Number 10 has denied Boris Johnson was absent from emergency coronavirus meetings because he was putting together a biography of William Shakespeare.
It comes after The Sunday Times reported government officials fear Mr Johnson's former chief adviser, Dominic Cummings, will make such an allegation when he gives evidence to a group of MPs this week.
The prime minister missed five COBRA meetings on COVID-19 at the beginning of last year.
According to the newspaper, some within the Cabinet Office are concerned Mr Cummings will make the accusation that Mr Johnson was working on a book at the time as the prime minister needed the money from it to fund his divorce from Marina Wheeler, his second wife.
However, the prime minister's official spokesman on Monday said he was not aware of Mr Johnson having spent any time researching a book on Shakespeare since entering Number 10.
The spokesman added Mr Johnson has been "ensuring the public are kept as protected as possible during this global pandemic".
Asked if work on a Shakespeare biography was responsible for Mr Johnson missing COBRA meetings in January 2020, the spokesman said: "No, and I think there are a number of incidents I can run you through where COBRAs have been chaired by relevant secretaries of state."
Mr Cummings's appearance before a joint COVID inquiry by two House of Commons committees on Wednesday follows months of feuding between him and Downing Street.
Since leaving Downing Street in November last year, Mr Cummings has used Twitter and his blog to make a series of allegations about Mr Johnson's handling of the COVID crisis, including his claim at the weekend that ministers originally pursued a strategy of "herd immunity".
But Mr Johnson's spokesman said: "Herd immunity from infection has never been government policy."
Asked if the prime minister believed Mr Cummings was a liar, the spokesman said: "I haven't asked him that question."
Mr Johnson was first reported to have signed a £500,000 book deal to write a biography about Shakespeare in 2015.
At the time, the book was said to be due for publication to mark the 400th anniversary of Shakespeare's death in 2016.
In April 2019, before Mr Johnson became prime minister, publisher Hodder & Stoughton said the still-to-be-completed book would be published in April 2020.
But, later in 2019 on the day Mr Johnson became prime minister, the publisher admitted it had no plans to publish "Shakespeare: The Riddle of Genius" for the "foreseeable future".
According to his register of financial interests as an MP, Mr Johnson regularly receives royalties from Hodder & Stoughton and other publishers for books he has previously written, which include a biography of Winston Churchill.