The BBC said the Prime Minister’s televised statement on new coronavirus restrictions in England was watched by an average audience of 15.6 million viewers.
Mr Johnson will reportedly use the press conference to explain further the reasoning behind the latest lockdown measures.
Labour leader Sir Keir Starmer will also make a televised statement responding to the Prime Minister’s announcement of a new lockdown for England at 7pm on BBC1, the party has said.
It comes after a warning from senior cabinet minister Michael Gove that the tough measures may have to remain in place until March.
The Treasury said the payments are expected to cost £4 billion and support 600,000 business properties across the UK.
Another £594 million will be made available to councils and devolved nations to support businesses not covered by the new grants.
People will be required to stay at home except in specific circumstances, including for food shopping, caregiving, medical care, exercise, and fleeing violence.
The Prime Minister also said everyone should work from home unless it is impossible to do so, for example those in construction or key workers.