UK Prime Minister Boris Johnson's former chief adviser released social media exchanges that appear to show Britain's leader criticising Health Secretary Matt Hancock's response to the pandemic.
Mr Johnson appears to describe Mr Hancock's performance as "totally useless" and "hopeless".
Dominic Cummings, who has accused Mr Hancock of being a serial liar, on Wednesday published a screenshot of a WhatsApp exchange.
The conversation, which appears to be between Mr Johnson and Mr Cummings, took place on March 3 last year.
Mr Cummings compares the number of tests carried out by the US per day to the smaller number performed by the UK.
Mr Johnson purportedly responded: “Totally useless.”
Mr Cummings left Downing Street in November last year after a power struggle between several special advisers.
Appearing before MPs last month, the former chief aide said Mr Hancock should have been sacked for lying to Mr Johnson a number of times.
Mr Hancock denied that he had ever lied to Mr Johnson.
He said it was telling that Mr Cummings had not provided evidence to back up his claims.
However, Mr Cummings said in Wednesday’s blog post that ministers were trying to “rewrite history”.
He published another private message about the struggles to procure ventilators for Covid-19 patients.
“It’s Hancock. He has been hopeless,” Mr Johnson appears to say in the March 27 message.
In another message, Mr Johnson describes the shortages of personal protective equipment as "a disaster", and questions whether he should hand some responsibility to Cabinet Office Minister Michael Gove.
“I can’t think of anything except taking Hancock off and putting Gove on,” Mr Johnson purportedly said.
Mr Cummings accused Mr Johnson of supporting the fiction that he was in agreement with Mr Hancock throughout the pandemic, saying the WhatsApp messages show otherwise.
Mr Johnson has not commented on the release of the messages and was not asked about them by opposition MPs in Prime Minister's Questions on Wednesday.