The latest figures showed a further 1,631 Britons had died within 28 days of a positive COVID-19 test, taking the total to 100,162 people, while another 20,089 new cases were also recorded on Tuesday.
Britain is the fifth country in the world to record 100,000 virus-related deaths, after the United States, Brazil, India and Mexico, and by far the smallest.
The 100,162 deaths registered are more than the country's civilian death toll in World War II and twice the number killed in the 1940-1941 Blitz bombing campaign, although the total population was lower then.
In December, Britain became the first country in the world to approve Pfizer's COVID-19 vaccine.
Britain reported its first cases of the disease nearly a year ago, on 29 January 2020 but Prime Minister Boris Johnson was initially relaxed about introducing measures to tackle the spread. Johnson's Conservative government is accused by many scientists of waiting too long to impose a lockdown in March as infections were rising exponentially. Leading epidemiologists say acting a week sooner might have cut the death toll in half.
CDC: Severe reactions to Moderna vaccine rare
The majority of the 100 million doses are earmarked for delivery in the first quarter of the year. Most of the cases involved people with a history of allergic reactions.
Many more deaths would follow before a vaccination programme began to take effect, England's chief medical officer said.
Professor Sir David Spiegelhalter, chair of the Winton Centre for Risk and Evidence Communication at the University of Cambridge, said: "ONS data show that over 100,000 people in the United Kingdom had already died with Covid on their death certificate by January 7, almost three weeks ago".
Mr Johnson promised that "we will come together as a nation to remember everyone we lost and to honour the selfless heroism of all those on the frontline who gave their lives to save others" once the pandemic was over.
"Of course we will learn lessons in due course and of course there will be a time to reflect and to prepare for the next pandemic", Johnson said last week. "The virus is still spreading and we're seeing over 3,500 people per day being admitted into hospital", he added.