U.S. businesses paid less last month for energy and wholesale goods, as the country's wholesale prices dipped 1.0 percent on the seasonally adjusted basis, marking the biggest fall since July 2009, the Labor Department said Wednesday.

This was the second decline in a row since December 2011 of the Producer Price Index, which measures price changes at factory gates.

The index moved down 0.2 percent in April and remained flat in March, the department said.

Energy prices dropped 4.3 percent in May, while food costs fell 0.6 percent.

Excluding the volatile food and energy sectors, the so-called "core" wholesale prices rose 0.2 percent in May from the previous month.

The wholesale prices have risen 0.7 percent over the past 12 months ending May.