Production by automakers in the UK plummeted last month as factories were halted and shifts rescheduled to brace for the planned March 28 Brexit, data from the Society of Motor Manufacturers and Traders showed.
A total of 70,971 vehicles were produced last month, 45% fewer than a year earlier.
Manufacturing for domestic and overseas markets fell 44% and 45% respectively, as most major companies brought forward and extended production stoppages normally scheduled for the summer holidays, the trade body said in a statement.
Overall European car sales declined for an eighth straight month in April amid weak demand in the UK, where Brexit uncertainty prompted consumers to delay big-ticket purchases.
Registrations fell 0.5% to 1.34m cars in the EU and EFTA from 1.35m a year earlier, according to industry association ACEA.
The UK's departure from the European Union did not materialize in March, and what kind of divorce the country wants is not yet clear.
Should the UK eventually leave the EU with a favorable deal and a substantial transition period, the slide is expected to slow by year-end, according to SMMT.
Production in the UK may fall about 11% this year from 2018, SMMT said, citing a projection by research firm AutoAnalysis.