The future of public health in England is set to be announced later by Health Secretary Matt Hancock.
Mr Hancock is due to deliver a speech at the think tank Policy Exchange titled The Future of Public Health.
It comes amid reports that Public Health England (PHE) is to be axed.
The Government has faced criticism over the prospect of breaking up the health body in the middle of a pandemic.
Ministers have also been accused of using PHE as a “scapegoat” for other failings in the crisis.
On Monday, the boss of the embattled organisation apologised to staff that news of the demise of the organisation was leaked.
Duncan Selbie, chief executive of PHE, said he was “sorry beyond words” the future of the body was briefed to the media before his staff were told.
A story placed with The Sunday Telegraph suggests that the Covid-19 response work of PHE is to be merged with NHS Test and Trace to form a new body designed specifically to deal with pandemics.
Other aspects of its operations, such as tackling obesity, could be handed over to councils and family doctors, the newspaper said.
According to The Sunday Telegraph, a new Institute for Health Protection will become “effective” from next month, although the merger will take until next spring to complete.
Other reports suggest Baroness Dido Harding, who leads the NHS Test and Trace system, will be the interim chief of the new agency.
Mr Selbie said that no organisation could get “everything right” and he praised staff for their efforts during the pandemic.
The note to staff, seen by the HSJ, states: “I am sorry beyond words at the way that decisions about our future have been briefed to the media before I have had the chance to explain them.
“The Prime Minister and Secretary of State wish to recreate an organisation with a sole focus on health protection and to bring together our health protection services with the budgets and people of the NHS test-and-trace programme to create a new national institute for health protection.”
He added: “Any organisation that says it got everything right is wrong and no public health body enters a pandemic expecting to look the same as a consequence.
“However, no one remotely close to our work of the past eight years, and since January on the pandemic would agree with the headlines that this change reflects ‘pandemic failure’ on our part.
“Certainly this is not what the Secretary of State believes or says in public or private.
“No public body has done more to protect the health of the people than PHE nor has more reason to be proud of its contribution.”
Responding to reports that Public Health England is to be replaced, a No 10 spokesman said on Monday: “We have always said we must learn the right lessons from the crisis and act to ensure Government structures are fit to cope.
“But I would make the point that PHE have played an integral role in our response to this unprecedented pandemic, working on important issues such as detection, surveillance, contact tracing and testing.”
But critics said if ministers are unhappy with PHE’s performance, they have only themselves to blame as it is directly under ministerial control.
Unite national officer for health Jackie Williams said: “It is clear that Public Health England and its dedicated staff are being lined up to be the fall guy for continual bungling by Boris Johnson and his ministers since coronavirus emerged at the beginning of the year.”
Karen Middleton, chief executive of the Chartered Society of Physiotherapy, said: “There have clearly been failings in handling the Covid pandemic, but scapegoating PHE is unfair and potentially dangerous.
“A range of people and agencies are accountable for the handling of the pandemic, not just PHE.
“This feels like a crude attempt to shift blame.”
Christina Marriott, chief executive of the Royal Society for Public Health, said: “We question the timing of an announcement to scrap our national public health agency in the midst of a global pandemic and before any public inquiry has started, let alone reported.”