LONDON — As Britain closes in on 100,000 reported cases of the coronavirus — a solemn milestone in a contagion that has ravaged its political leadership — a raft of new statistics suggests that the government is undercounting the human, and economic, cost of the epidemic.

The government’s Office of National Statistics released data on Tuesday revealing that the death toll from the virus could be at least 10 percent higher than the official toll of 12,107 because that number does not take into account people who die in nursing homes or in their own residences.

At the same time, the Office for Budget Responsibility, a fiscal watchdog group, said the lockdown could shrink Britain’s economy by 35 percent in the second quarter and throw two million people out of work — a prediction even worse than the government’s darkest warnings.

Taken together, these new numbers cast a grim shadow over Britain’s response to the epidemic, which has already been dogged by shortfalls in testing and questions about the supply of ventilators and protective gear.