The depressed figures reflect the impact of low growth and budget reforms on business and household spending in the European Union.
The data casts a shadow over some signals that the EU economy may be recovering slowly, since in several EU countries the manufacture of cars is an important indicator of production, exports and consumer confidence.
In the first six months of the year, sales fell by 6.6 percent to a total of 6.205 million, although the British market, the only one to expand, grew by 10.0 percent.
The EU car market has been shrinking for 18 months, with one small upward blip in April. This reflected the fact that April this year had two more working days than April last year.
The figures for June were gloomy. Sales fell by 5.6 percent on a 12-month comparison across the European Union to a total of 11.3 million, the lowest volume since 1996.
Sales in France fell by 8.4 percent, in Italy by 5.5 percent and in Germany by 4.7 percent, the figures from the European Automobile Manufacturers' Association showed.
In Spain the fall was contained to 0.7 percent by government help for the purchase of new cars, but the overall Spanish new car market is at the lowest level for 20 years.
Spain is in the grip of recession and high unemployment as it struggles to reform its public finances and economy with tax rises and budgets cuts.
The exception again was Britain where sales have risen in recent months and grew again by 13.4 percent in June.
The data covered 26 of the 27 countries comprising the European Union in June, with the exception of Malta for which data was not available.