Sales of GM's Silverado plunged 16% in December. Photo credit: General Motors

All major automakers will be releasing December sales figures today and thus far General Motors Company (NYSE:GM) appears to be the biggest loser with its deliveries down 6.3% compared to a year ago. Further, General Motors' retail and fleet sales were down 6% and 9%, respectively. 

Looking at General Motors' four brands, Chevrolet and Buick were the worst performers in December with year-over-year changes of -8.1% and -6.6%, respectively. GMC and Cadillac turned in better performances, although both were still down from last December by 1.8% and 0.5%, respectively. Said Kurt McNeil, vice president, U.S. sales operations, in a company press release:

December started a little slow but sales were stronger later in the month, especially in the week between Christmas and New Year's. We didn't make any big changes to our 'go-to-market' strategy during the month, which is to offer competitive incentives and market aggressively, and we are carrying good momentum heading into January.

Looking at individual models, investors will surely be disappointed in December sales figures from General Motors' two most profitable vehicles: the Silverado and Sierra. Those two full-size trucks posted sales declines of 16% and 4.6%, respectively.

Overall, GM says it sold more than 230,000 vehicles last month, down from nearly 246,000 a year ago. For the full year, GM sales rose to nearly 2.8 million vehicles, a 7.3% increase.

There were a few bright spots in General Motors' December figures. The Chevrolet Corvette had its best December sales since 2006 with a 132% increase over last year. The GMC Acadia posted a sales increase of 53%, which is good enough for its best-ever December. Also, the redesigned Malibu and all-new Impala were up 33% and 10%, respectively -- giving investors some hope that its redesigns are significantly improving sales on most models.

Looking ahead, General Motors will have launches including all-new large SUVs for its Cadillac, GMC, and Chevrolet brands. It will also be unveiling all-new mid-size pickups for Chevrolet and GMC brands, while Ford has refused to re-enter the mid-size pickup market.

-- Material from The Associated Press was used in this report.