The company had sold 45,297 units in the same month previous year, the company said in a statement.
In December, M&M's domestic sales stood at 36,881 units as against 42,307 in the same month previous year, down 12.82 per cent.
Total sales of passenger vehicles, including Scorpio, XUV500, Xylo, Bolero and Verito, stood at 16,436 units during the month as against 22,761 in December 2012, down 27.78 per cent.
Sales of the company's four-wheel commercial vehicles were up 5.05 per cent at 14,399 units as against 13,706 units in December 2012, it said.
Its three-wheeler sales were up 7.62 per cent at 5,606 units during December 2013 as against 5,209 units in the same month previous year.
M&M's exports were down by 8.69 per cent to 2,730 units during the month from 2,990 units in December 2012.
Commenting on the sales performance, M&M Chief Executive (Automotive Division) Pravin Shah said: "During the first nine months of the current fiscal, the auto industry has seen a negative growth due to sustained deceleration in economic activity and consequent weakness in consumer and business sentiments."
While the immediate turnaround in the auto industry is not expected without certain policy corrections and support, the worst seems to be over, he added.