Data shows that 16,088 vans, trucks, buses and coaches were built in Britain in January, representing a year on year decrease of 18.8%.
Output for both domestic and export markets saw double digit declines, falling by 19.7% and 18.5% respectively.
However, overseas demand continued to drive volumes, with almost seven out of every 10 (67.9%) CVs built in the UK destined for global customers.
SMMT chief Mike Hawes said: "January’s decline in UK commercial vehicle production continues 2017’s downward trend, and is yet further evidence of falling confidence in the sector.
"To restore certainty to manufacturers and operators, encourage fleet investment and keep trade flowing freely with our key global customers – most of which are in the EU – we need urgent clarity on the future trading arrangements between Britain and Europe."
