The Consumer Prices Index (CPI) rate of inflation climbed to 2.6% last month, from 2.4% in June.
It represents the first rise in inflation in four months.
Analysts had anticipated a marginal fall in the CPI rate, which was as high as 5.2% in September last year before starting to fall.
The Retail Prices Index climbed to 3.2%, from 2.8% in June.
The Bank of England has previously forecast that inflation would fall to around 2.1% in the final quarter of 2012, but then might rise slightly before averaging below the 2% target from late 2013 onwards.
