After rising by 0.5% in the year to March 2016, The Consumer Prices Index rose by 0.3% in the year to April 2016.
This was compared with a 0.3% rise in the year to February.
The ONS stated: "From late 2015, the rate began to increase gradually from close to zero. The drop in April 2016 is the first fall since September 2015.
"Falls in air fares and prices for clothing, vehicles and social housing rent were the main contributors to the decrease in the rate.
"These downward pressures were partially offset by rising prices for motor fuels and for certain recreational goods and cultural services, and by food prices, which were unchanged between March and April 2016, having fallen between the same two months a year ago."
Nick Dixon, investment director at Aegon UK, said: “While inflation was weak in April, we may be closer than forecasts indicate to the inflection point when inflation starts to accelerate.
"A combination of rising energy costs, higher US rates, and lower £ sterling could bring inflation forward and trigger rising interest rates before the end of 2016.”
CPIH (not a National Statistic) grew by 0.6% in the year to April 2016, down from 0.7% in March.