In a televised briefing on Monday, the chief medical officer for England will say the country faces a “very challenging winter”, with the current trend heading in “the wrong direction”.
Boris Johnson spent the weekend with senior ministers and advisers discussing what action to take as the rise in the number of new cases showed no sign of slowing.
It is thought the Prime Minister could set out new measures in a press conference as early as Tuesday.
Prof Whitty, who will appear alongside the Government’s chief scientific adviser Sir Patrick Vallance, will explain how the virus is spreading in the UK and the potential scenarios that could unfold as winter approaches.
They will draw on data from other countries such as Spain and France, which are experiencing a second surge, to underline how their experience could be replicated in the UK.
Prof Whitty is expected to say: “The trend in the UK is heading in the wrong direction and we are at a critical point in the pandemic.
“We are looking at the data to see how to manage the spread of the virus ahead of a very challenging winter period.”
Ministers were reported to be split on how far any new restrictions should go, with Chancellor Rishi Sunak said to be resisting controls which could further damage the economy.
During a series of broadcast interviews over the weekend, however, Health Secretary Matt Hancock refused to rule out a second national lockdown in England, if people fail to follow the social distancing rules.
He said he feared cases could go “shooting through the roof” with more hospitalisations and more deaths.
Meanwhile London mayor Sadiq Khan is to meet council leaders in the city on Monday to discuss possible new restrictions in the capital, which they would then put to ministers.
“The situation is clearly worsening,” a spokesman for the mayor said.
“The mayor wants fast action as we cannot risk a delay, as happened in March. It is better for both health and business to move too early than too late.”
Another 3,899 lab-confirmed cases of coronavirus in the UK were announced on Sunday, while a further 18 people died within 28 days of testing positive, bringing the UK total to 41,777.
The latest figures came after the Government announced anyone in England refusing to obey an order to self-isolate could face a fine of up to £10,000 and just days after the “rule of six” – banning social gathering of more than six people – came into force.
Mr Johnson has been desperate to avoid another nationwide lockdown amid concerns about the economic damage it will inflict just as activity was beginning to pick up again.
However, as of Tuesday, about 13.5 million people across the UK will be facing some form of local restrictions, including 10pm curfews for pubs and restaurants, as the authorities grapple with the disease.
Among the measures being considered by ministers is a temporary two-week “circuit break”, with tighter restrictions across England in an attempt to break the chain of transmission.
However, the Government is facing resistance from some senior Conservative MPs concerned that ministers are taking increasingly stringent powers with little or no parliamentary scrutiny.
Sir Graham Brady, chairman of the powerful Tory backbench 1922 Committee, said he will table an amendment which would require the Government to put any new measures to a vote of MPs.
Sir Keir Starmer said Labour would support any new measures but warned that a second national lockdown was becoming more likely because the Test and Trace programme was in a state of “near collapse”.