European car registrations fell 8.7% year-on-year in December, new figures show today.
Sales at all major carmakers except Daimler and Jaguar Land Rover contracted as the introduction of tougher new emissions tests continued to weigh on demand.
Registrations fell to 1.04 million cars in the European Union (EU) and European Free Trade Association (EFTA) countries, the Brussels-based Association of European Carmakers (ACEA) said.
This was down from 1.14 million a year earlier.
The drop came after the tougher new Worldwide Harmonised Light Vehicle Test Procedure (WLTP) became mandatory from the start of September, forcing some carmakers to halt deliveries of some models that had yet to be certified.
European car sales had surged in the month before the new procedure became effective and have declined every month since.
"In December 2018, the EU passenger car market declined for the fourth month in a row, continuing the downward trend that started with the introduction of WLTP in September," the industry group said in a statement.
Full-year sales were flat at €15.6m, with the sale slumps in the last four months of the year weighing on previously improving sentiment in the European car market.
European car sales returned to annual growth in 2014 after a six-year slump during which registrations fell to their lowest in decades.
In December, sales at Europe's biggest carmaker Volkswagen fell 9.3%, with demand for premium carmakers Audi and Porsche dropping 19.5% and 16.5% respectively.
France's Renault recorded a 16.7% decline, while alliance partner Nissan saw a 28.9% drop.
Sales at Japan's Toyota fell 10.4%, at Germany's BMW by 8.7% and at France's PSA Group by 6%.
European registrations in the month were down 2.5% at Italo-American Fiat Chrysler, despite a nearly 36% increase in sales of its popular Jeep SUV brand.
Sales at Germany's Daimler increased 8.5%, helped by a nearly 11% rise in its premium brand Mercedes, while demand for vehicles from the Jaguar Land Rover group increased 9.7%.
All five major markets except for Italy recorded sales contractions last month, led by France, where registrations fell 14.5%. Italian sales increased 2%.