Consumer price index inflation rose to 3.6 per cent in June, up from 3.4 per cent in May and the highest since January 2024, the Office for National Statistics said on Wednesday.
The increase was unexpected, with most economists forecasting inflation to remain unchanged at 3.4 per cent.
Annual food price inflation hit the highest level since February 2024, while transport costs also pushed up the cost of living.
ONS acting chief economist Richard Heys said: "Inflation ticked up in June driven mainly by motor fuel prices which fell only slightly, compared with a much larger decrease at this time last year.
"Food price inflation has increased for the third consecutive month to its highest annual rate since February of last year.
"However, it remains well below the peak seen in early 2023."
Chancellor Rachel Reeves said there was "more to do" to help bring inflation down.
"I know working people are still struggling with the cost of living," she said.
"There is more to do and I'm determined we deliver on our Plan for Change to put more money into people's pockets."
The surprise increase in inflation will be watched closely by the Bank of England before its next interest rate decision in August.
Policymakers are widely expected to cut rates again in August, from 4.25 per cent to four per cent, given a slowing wider economy, but the latest unexpected rise in inflation may see the Bank tread cautiously further out, according to experts.
The figures come after the economy shrank by 0.1 per cent in May, following a 0.3 per cent fall in April and leading to fears of a contraction overall in the third quarter.
Jobs figures on Thursday are expected to show a further slowdown in wage growth, which might help smooth the path for a rate cut.
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