British car manufacturing output plummeted by almost half in April, according to figures published by the Society of Motor Manufacturers and Traders (SMMT).

These show that 70,971 cars rolled off production lines in the month (down 44.5% compared with April 2018), as factory shutdowns — rescheduled to “mitigate against the expected uncertainty of a 29 March Brexit” — took effect in many plants across the UK.

Manufacturing for domestic and overseas markets fell by 43.7% and 44.7% respectively, as most volume manufacturers brought forward (and extended) production stoppages normally scheduled for the summer holiday period.

Moreover, the SMMT says the shift in shutdown was part of a raft of costly and on-going contingency measures intended to protect business when the UK leaves the customs union and single market.

In the first four months of 2019, 127,240 fewer cars were built compared with the same period in 2018 — a decline of 22.4% — with similar percentage falls in production for the UK and for export.

Mike Hawes, SMMT chief executive (www.smmt.co.uk), said: “These figures are evidence of the vast cost and upheaval Brexit uncertainty has already wrought on UK automotive manufacturing businesses and workers.

“Prolonged instability has done untold damage, with the fear of ‘no deal’ holding back progress, causing investment to stall, jobs to be lost and undermining our global reputation.”

The picture was even worse for UK commercial-vehicle production, which saw a drop of 70.9% in April (compared with April 2018).

Just 2,162 vans, trucks, buses and coaches left production lines, as planned shutdowns to prepare for model changeovers resulted in the substantial drop in output.

Production for both home and overseas markets experienced significant decline, falling by 27.1% and 89.9% respectively.

The proportion of CVs exported fell to 24.3%, the lowest level on record.

That said, production volumes for the first four months were up 10.3% compared with 2018, driven by a rise in demand from the domestic market.

However, exports continue to drive output, making up nearly 60% of production in the first four months.

Meanwhile, British engine manufacturing fell by 23.4% in April to 177,925 units (232,400 in April 2018), with production for home and international markets down by 41.1% and 12.8% respectively.

Exports continued to drive production, with seven in 10 engines shipped to over-seas factories.