Dominic Cummings has shared a photo of a whiteboard laying out when he claims was Government's Covid plan - which says 'who do we not save?'.
The ex-adviser is being grilled by select committee MPs on Wednesday over his role in the pandemic.
Mr Cummings had spent the days in the run-up to his appearance dripping information on his Twitter feed - including the photo.
He tweeted an image of the whiteboard, which was apparently completed in March last year in No10.
He said the scribblings were the "first sketch of a Plan B, PM study".
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Several concerns are raised, including the need to prevent a collapse of the NHS and the prospect of there not being a vaccine in 2020.
But one noticeable line at the bottom has caused a stir - where it says 'who do we not save?'.
'Not' has been underlined.
In his hearing, Mr Cummings the described chaos in Downing Street in the days leading up to the first Covid lockdown.
He at one point compared the situation to a "scene from Independence Day" - the 1996 disaster movie.
Mr Cummings said that on the evening of March 13 - when the whiteboard was supposedly filled in - it was realised that a meeting would need to be held with Mr Johnson to explain "we're going to have to ditch the whole official plan, we're heading for the biggest disaster this country has seen since 1914".
He said the "second most powerful official in the country" at the time, Helen MacNamara, who was Deputy Cabinet Secretary, walked into the room and said: "I've just been talking to the official Mark Sweeney who is in charge of co-ordinating with the Department of Health. He said, quote, 'I've been told for years that there was a whole plan for this. There is no plan. We're in huge trouble'."
Mr Cummings said she told him: " I think we are absolutely f*****, I think this country is headed for disaster, I think we're going to kill thousands of people."
Mr Cummings said he told her: "I think you're right. I think it is a disaster."
He said that on March 14, the Prime Minister was told: "You are going to have to lock down."
But Mr Cummings added: "But there is no lockdown plan. Sage haven't modelled it, DH don't have a plan, we are going to have to figure out and hack together a lockdown plan."
He added: "This is like a scene from Independence Day with Jeff Goldblum saying, 'the aliens are here and your whole plan is broken, and you need a new plan'... that is what the scene was like that morning, with Ben Warner in the Jeff Goldblum role.
"He took the Prime Minister through all the graphs, and through the NHS graphs, and showed him that the system is thinking this is all weeks and weeks and away... but this is all completely wrong... The NHS is going to be smashed in weeks."
Mr Cummings said it was a "huge failure" on his own part that he did not push harder for an earlier lockdown.
He said: "I bitterly regret that I didn't kind of hit the emergency panic button earlier than I did.
"I think, in retrospect, there's no doubt that I was wrong not to."
He said he was "incredibly frightened" to say the official plan was wrong in case he himself was wrong.
