Boris Johnson's former chief adviser gave evidence about the pandemic to MPs on Wednesday during a marathon seven-hour session.
Johnson, Cummings said, was unfit for his role, while his greatest criticism was reserved for Hancock who he said had repeatedly lied to such an extent that the country's top civil servant lost confidence in his honesty.
Boris Johnson's former aid described Matt Hancock as "completely incapable of doing the job".
Also on Thursday, Johnson said he disagreed with his former aide Cummings' claim that tens of thousands of people died unnecessarily because of the government's inaction on Covid-19.
Mr Johnson has previously denied making the comment, which Mr Cummings told MPs he heard from the Prime Minister in his Downing Street study.
Mr Cummings said Matt Hancock had promised to put in place hospital-to-care-home testing in time for March 2020.
"This has been an incredibly hard series of decisions, none of which we've taken lightly", he said.
Responding to Mr Cummings' claims about it being "nonsense" to say care homes were shielded, Mr Johnson said: "We did everything we could to protect the NHS and to protect care homes as well".
The prime minister's former top adviser, Dominic Cummings, turned his fire on ministers in an explosive seven-hour evidence session before United Kingdom lawmakers on Wednesday during which he described Boris Johnson as "unfit for the job".
The health spokesman for the opposition Labour Party, Jonathan Ashworth, said the government had questions to answer, whether or not Mr Cummings' testimony was true.
With nearly 128,000 deaths, the United Kingdom has the world's fifth highest official Covid-19 toll, far higher than the government's initial worst-case estimates of 20,000.
A mass vaccination campaign that started in December has brought confirmed cases and deaths down sharply, though Britain is now reckoning with a more transmissible new strain of the virus first identified in India. Johnson has announced there will be a full inquiry into the government's handling of the crisis, but not until the spring of 2022. It is spreading across the country and scientists expect it to become the dominant variant in Britain, but they say existing vaccines appear to work against it.
"We take decisions as fast as we can but we have to weigh the data", he said.