Covid-19 deaths could be twice as high over the winter as they were in the first wave of the pandemic, PM Boris Johnson is expected to warn MPs.
In a Parliamentary statement he will say there is “no alternative” as he seeks to win support for the planned four-week lockdown across England.
But Mr Johnson will explain he was “right to try every possible option” before ordering people to stay at home.
Labour has said it will back the lockdown but criticised the delay.
Mr Johnson announced at a Downing Street news conference on Saturday that strict measures would be imposed across England from Thursday, closing pubs, restaurants, gyms, non-essential shops and places of worship.
Full details of the regulations are expected to be published before MPs vote on the measure on Wednesday.
However, Housing Secretary Robert Jenrick confirmed that moving house will still be allowed during the restrictions, adding that removals firms, estate agents and tradespeople can continue to work but must follow Covid safety guidelines.
The prime minister is due to tell MPs that the government will “seek to ease restrictions” on 2 December and return to the current three-tier system.
On Sunday, Cabinet Office minister Michael Gove said the lockdown could be extended if it took longer to bring the transmission rate of the virus down.
Mr Johnson faces a rebellion from several senior Tory MPs, including Sir Graham Brady, chairman of the 1922 Committee of backbenchers.