Data shows 122,116 cars were made compared to 149,324 in the same month last year – a decrease of 18.2%.
The SMMT says that the late Easter bank holiday affected production.
However, year-to-date production remains strong. A total of 593,796 cars have been made so far this year compared to 587,714 in 2016 – a 1% increase.
Says SMMT chief Mike Hawes: “Car production fell significantly in April due to the later Easter bank holiday weekend which reduced the number of active production days that month and also due to unplanned production adjustments.
“Overall, British car manufacturing remains in good health with the production outlook still very positive and significant new models due to go into UK production shortly.
“To guarantee future growth and investment into our industry and its vital supply chain, however, we need the next government to safeguard the conditions that have made us globally competitive, keeping us open and trading and delivering an ambitious industrial strategy for our sector.”
UK car manufacturing falls by nearly a fifth
UK car manufacturing dropped by almost a fifth in April, according to the Society of Motor Manufacturers and Traders (SMMT).