UK inflation fell to a five-year low of 1.2% in September from 1.5% the month before, official figures show.
The rate, as measured by the Consumer Prices Index, is the lowest since September 2009, when it was 1.1%.
Lower energy and food prices helped to cut the rate, while the Office for National Statistics (ONS) also cited cheaper transport costs as a factor.
The news sent the pound lower as analysts said a rate rise was now not likely until well into next year.
The Retail Prices Index measure of inflation fell to 2.3% from 2.4% in August.
Read more: Rate timing