FOR the first time since World War I, an imported vehicle has outsold a locally assembled car to be the nation's top-selling new car for the year.

The Holden Commodore's record 15-year winning streak was brought to an end by a Japanese Mazda.

According to preliminary figures obtained by the Herald, the Mazda3's victory was sealed in December when it edged further ahead of the Commodore by about 600 sales after swapping position six times and being separated by just 20 transactions at the end of June.

Ten years ago, large cars such as the Holden Commodore and Ford Falcon accounted for more than one third of the new vehicle market. Now small cars outsell them by more than three-to-one.

Last year was the most hotly contested battle for top-seller status since new-vehicle sales records were kept and marks the end of an era for Holden.

No other automotive nameplate has had such a winning streak; the closest was the Ford Falcon's seven-year dominance over the Commodore between 1982 and 1988. A long line of General Motors Holden vehicles were top sellers from 1950 to 1981.

The British-designed Austin A40 was the top-seller in 1948 and 1949 (while the original Holden was gaining momentum) but it was assembled locally, as were most cars in the post-war era, to avoid high imposts designed to protect local industry.

''A fully imported car hasn't led the Australian new-car market for as far back as I can remember,'' veteran automotive journalist, historian and author, Pedr Davis, 82, told the Herald. ''Of course, the records are gone but I would say you'd have to go back to pre-World War I. Even Model T Fords were assembled in Australia.''

Official sales figures for 2011, due to be released at midday tomorrow, are also expected to show the worst year on record for the Ford Falcon, dipping below 20,000 after hovering around 30,000 a year for the past four years - a dramatic fall from its peak of 81,000 in 1995.

The Falcon's weakening sales will prompt further speculation about the future of local production of Australia's oldest continuous automotive nameplate. Sales of locally made Mitsubishi cars dipped below 20,000 just four years before its Adelaide factory was closed.

This reporter is on Twitter: @JoshuaDowling