Shares in car dealership Pendragon plunged as much as 20pc after it warned over profits because of a new vehicle emissions testing regime.

Pendragon, one of the largest car dealers in the UK, said the introduction of the worldwide harmonised light vehicle test procedure (WLTP) had caused “significant disruption” to sales of new cars and “uncertainty” over the supply of stock.

WLTP was introduced in the wake of the VW “dieselgate” emissions scandal. The new tests - which came into force in September - aim to give a more accurate measure of the pollution produced by cars in real-world driving conditions than the previous regime.

However, a bottleneck in testing facilities means manufacturers have been unable to get all their cars examined under WLTP conditions, and without doing so the vehicles cannot be sold.

Many car makers rushed through sales in August to beat the new regime, but dealers are now unable to get enough cars to sell.