The number of bus passenger journeys in England fell by 238 million in the year ending March 31, figures show.
The total of 4.07 billion was a 5.5% reduction on the previous 12 months.
The Department for Transport (DfT) said the fall can “largely be attributed” to the coronavirus pandemic.
Although the national lockdown did not begin until March 23, bus companies “started seeing declines in journeys in the preceding weeks”, the DfT added.
Graham Vidler, chief executive of the Confederation of Passenger Transport, which represents the bus industry, said: “This drop in passenger numbers reflects that in the weeks before lockdown we had already begun to see people deciding to travel less as a result of Covid-19.
“Following the stay-at-home message we also saw bus passenger numbers drop to 10% of normal in a matter of days.”
Mr Vidler urged the Government to ensure “we don’t lock in the increase in car use we have seen during the pandemic” by introducing measures which “focus on getting people back on to the bus”.
These include cutting bus journey times and giving local authorities and operators “the tools to deliver the services passengers need”.
Separate DfT figures show bus use in Britain excluding London is at 56% of pre-pandemic levels, while car use has returned to 85%.