Matt Hancock allegedly sent a journalist a "menacing message" at 1am after his WhatsApp exchanges during the Covid pandemic were leaked this week.
Isabel Oakeshott, who was given the WhatsApp exchanges by the former Health Secretary while they were collaborating on his pandemic memoir, said it was clear that Mr Hancock was not happy after she gave him no advance notice about what she was doing.
The Telegraph published a string of stories based on more than 100,000 messages between Mr Hancock, aides and other top ministers during the pandemic.
Ms Oakeshott told TalkTV's Piers Morgan Uncensored: "I received a somewhat menacing message at 1.20 in the morning.
If you can't see the poll, click here
"I am not going to repeat what was in the message. I think you can easily surmise whether Matt Hancock is my friend at this point."
Today, Mr Hancock rejected the claim, saying: "This is not true."
It is understood that he did send her a message late at night as he had not been contacted before the publication of the stories.
Ms Oakeshott confirmed that she broke a non-disclosure agreement to pass on the messages but said she believed she was acting in the public interest as it could be years before the official inquiry into the pandemic reports.
"The reality is that this inquiry, which I think is absolutely critical, will likely not come up with any conclusions, left to the Government's own devices, perhaps for at least a decade or more," she said.
"This resource that I had is an extraordinary way to quickly get to the truth of what happened. I think the public interest is overwhelming."
The bombshell messages have revealed that Mr Hancock allegedly failed to follow advice to test all people entering into care homes during the pandemic.
The texts show Mr Hancock said he did not think committing to testing those from the community - including care home staff.
This was despite guidance from Chief Medical Officer Chris Whitty telling him there should be testing for "all going into care homes" in April 2020.
Testing was implemented for all people entering care homes in August 2020.
Mr Hancock's spokesman said the messages had been "doctored to create a false story" that the top Tory ignored clinical advice, adding: "This is flat wrong."
The spokesman said the tranche of messages offered a "distorted account" and were being "spun to fit an anti-lockdown agenda".
The explosive row calls into question the Government’s insistence that it was always "following the science" during the pandemic.
The revelations were reported by The Telegraph, which has obtained more than 100,000 WhatsApp messages sent between the-then Health Secretary and other ministers and officials during the pandemic.
They contain 2.3million words and more controversial details about major decisions made by officials are expected to be released in the coming days.
The messages are said to show the often casual approach that officials took in huge decisions including to close classrooms, introduce face masks in schools, as well as provide testing in care homes.
The key messages relating to the first bombshell revelation are between Mr Hancock and one of his aides, Allan Nixon.
On April 14 2020, at almost 6.30pm, Mr Nixon sent a message saying: "Just to check: officials are saying your steer is to remove the commitment to testing on admission to care homes from the community, but keep commitment to testing on admission to care homes from hospital. Is that right?"
Twenty-five minutes later, he messaged again: "Update: we can say in the doc that it’s our ambition to test everyone going into a care home from the community where care homes want (‘in the comings weeks’ is the suggested timeframe I’ve been told)."
Mr Hancock responded: "Tell me if I’m wrong but I would rather leave it out and just commit to test & isolate ALL going into care from hospital. I do not think the community commitment adds anything and it muddies the waters."
