UK commercial vehicle (CV) production fell 41.8% year on year in March to 5,219 units according to Society of Motor Manufacturers and Traders (SMMT) data.
Nationwide coronavirus lockdown measures forced plants to close part way through March 2020.
Output for the UK market fell 43.4% while export production declined 40.6% as the pandemic caused business closures and dented confidence around the world.
The EU, the UK's largest commercial vehicle market, saw a drop in exports of 43.3%, with 2,762 units shipped.
Year to date, commercial vehicle production fell 22.0% to 21,473 units.
An SMMT survey of the impact of the COVID-19 outbreak on UK automotive business showed 42.1% of all commercial vehicle manufacturers believe a full recovery from the crisis will take them at least a year with a third (36.8%) expecting a loss in revenue of 30% or more by the end of 2020.
Government initiatives such as the Coronavirus Job Retention Scheme (CJRS) have placed 57.7% of permanent staff in the CV manufacturing sector on furlough and able to return to work in due course.
Mike Hawes, SMMT chief executive, said: "Manufacturers have been hit hard by the pandemic and factory shut downs are costing the sector and economy billions.
"This means implementing a package of measures that supports the entire automotive industry, from retail through supply chains to vehicle manufacture."
He added the CV sector awaited guidance on safe restart of manufacturing and support operations.