Annual inflation, as measured by the Consumer Prices Index, was 1.5% in May compared with 1.8% in April, according to the Office for National Statistics.
It is the sixth consecutive month that inflation has been below the Bank of England's 2% target.
Falls in transport costs, notably air fares provided the largest contribution to the decrease in the rate.
The rate of inflation, as measured by the Retail Prices Index (RPI) fell to 2.4% in May from 2.5% in April.
Prices, however, are still increasing faster than average earnings, which rose 0.7% in the three months to April.
The ONS said the timing of Easter, which fell in April this year, was likely to have had an impact on the rate of inflation, particularly on travel costs, which rose sharply to coincide with the Easter holiday.
Lower rises in the costs of food and drink also helped to drive down the rate of inflation as tough competition among supermarkets drove down prices.
Separate figures from the Office for National Statistics showed that UK house prices leapt by 9.9% in the 12 months to April to reach a new high of £260,000.
Source - BBC News