WASHINGTON — U.S. retail sales fell in December, posting the biggest drop since September 2009 and delivering more evidence that last year’s holiday sales fizzled unexpectedly. Even e-commerce suffered a big setback.

The Commerce Department said Thursday that December retail sales fell 1.2 percent from November. They were up 2.3 percent from December 2017. Total retail sales for 2018 rose 5 percent from the previous year.

Excluding gasoline station sales, which swing widely as pump prices rise and fall, retail sales dropped 0.9 percent in December. Nonstore retailers, which include mail-order and e-commerce vendors, saw sales tumble 3.9 percent. That’s the most since November 2008.

The discouraging December report raises concern about whether the retail sales slowdown was just a blip or points to a more sustainable weakness in consumer spending. But many analysts, as well as an industry group, questioned the reliability of the data. The National Retail Federation said the government shutdown and the resulting delay in collecting the data made the results less accurate.

The stock market recorded big drops in December. And a partial government shutdown began Dec. 22 at the end of the holiday shopping season.

Jack Kleinhenz, chief economist at the National Retail Federation, said that the government’s sales figures tell an “incomplete story” and that the group will be in a better position to judge the reliability of the results when officials revise its 2018 data in coming months.

Separately, the NRF said holiday sales in the combined November and December period increased a lower-than-expected 2.9 percent as worries about the trade war with China, the government shutdown and stock market turmoil dampened shopper spending in December.