WASHINGTON (Reuters) - U.S. consumer prices were unchanged in April as expected, but recorded their largest 12-month drop since 1955, government data showed on Friday, as sluggish consumer demand limited companies' pricing power.

The Labor Department said its closely watched Consumer Price Index was flat after falling 0.1 percent in March. Compared to the same period last year, consumer prices fell 0.7 percent, the biggest 12-month decline since June 1955. In March, the year-over-year CPI rate fell 0.4 percent.

Core prices, which exclude food and energy items, rose a faster 0.3 percent versus a 0.2 percent increase in March. That compared to analysts' prediction for a 0.1 percent increase. Core prices rose 1.9 percent year over year after a 1.8 percent rise in March.

Energy prices fell 2.4 percent after dropping 3.0 percent the previous month. The food index fell 0.2 percent in April, the largest drop since May 2002 and the third straight monthly decline.

(Reporting by Lucia Mutikani, Editing by Andrea Ricci)