Cummings, a key strategist behind the Conservative Party's 2019 election victory and the campaign for Britain to leave the European Union, said he was posting the messages to back up his explosive allegations against Hancock in evidence given to lawmakers during select committee hearings in late May.
Commons leader Jacob Rees-Mogg has hailed Health Secretary Matt Hancock as a "successful genius" - after he was allegedly branded "hopeless" by the PM.
In a separate message about the struggles to procure ventilators for patients on March 27 previous year, Mr Johnson allegedly wrote: "It's Hancock".
In another message, Johnson blamed Hancock for the UK's difficulty in getting hold of ventilators.
More than one year on, it is not Mr Hancock that has little hope left, it is the public.
Asked on the BBC's Politics Live if he thought Mr Hancock was "hopeless", he said: "Absolutely not". In one exchange between the two Johnson called Hancock "totally f**king hopeless" for his handling of the Covid-19 outbreak.
"It's Hancock. He has been hopeless", the contact appearing to be Mr Johnson replied on March 27th previous year.
In another, he appeared to say his procurement of personal protective equipment had been a "disaster", and that he wanted to hand some of Mr Hancock's duties to Cabinet Office Minister Michael Gove.
He claims Number 10 and Mr Hancock, had "repeatedly lied about the failures last year" and accuses them of now trying to "rewrite history".
But Mr Cummings described the cabinet office as a "total shitshow" and said the move would "have a severe risk of making it worse not better". - British Prime Minister Boris Johnson's chief adviser Dominic Cummings is set to leave his position by early 2021, as a power struggle at the heart of government became public this week.
Mr Cummings, who was forced out of his role as chief aide to the prime minister at the end of a year ago, also claims a promised public inquiry into the Covid crisis would not fix the problems.
Among his explosive claims was his depiction of contrasting styles in the handling of key COVID meetings between Mr Johnson and Foreign Secretary Dominic Raab, who deputised for the prime minister after Mr Johnson fell seriously ill with COVID.
No 10 insisted Mr Johnson still has full confidence in the Health Secretary, with the Prime Minister's official spokesman simply replying "yes" when asked during a Westminster briefing.
Asked if the Prime Minister called Mr Hancock hopeless, the spokesman said: "I'm not planning to engage with every allegation put forward, the Prime Minister worked very closely with the health and care secretary throughout and continues to do so".
"It will not start for years and it is created to punt the tricky parts until after this PM has gone - unlike other PMs, this one has a clear plan to leave at the latest a couple of years after the next election, he wants to make money and have fun not "go on and on", writes Mr Cummings.
Mr Cummings published a series of screenshots purportedly showing WhatsApp exchanges between himself and the prime minister to combat what he said are "lies" from Downing Street.