Volkswagen could face $18bn fine over secret device that ‘intentionally cut emissions’ – but only when cars were being tested

US regulators have charged Volkswagen with manufacturing vehicles designed to evade government pollution controls, and said the German auto giant should urgently fix nearly 500,000 cars.

Volkswagen could face an $18bn penalty over the software made to meet clean-air standards during official emissions testing but which would intentionally turn off during normal operations, US and California regulators said.