UK inflation has jumped to its highest rate since March after energy prices were pushed up by the Iran war, according to official figures.

The Office for National Statistics (ONS) said Consumer Prices Index (CPI) inflation rose to 2.9% in July, up from a 15-month low of 2.6% in June.

It follows a 13% hike in Ofgem’s energy price cap last month, which increased the average gas and electricity bill by £221 to £1,862 a year.

Mike Hardie, deputy director for prices at the ONS, said: “Inflation rose in July, driven by a sharp increase in gas prices following this month’s change to the energy price cap.

“This was the largest rise in gas prices for almost four years.

“Other upward pressures included furniture prices falling by less than usual for this time of year, and also a smaller fall for clothing prices due to reduced discounting.”

The ONS said the steep rise in the energy cap, which follows a big jump in wholesale gas prices, was only partly offset by last month’s lower crude oil costs, which had fallen sharply month-on-month in July amid hopes of a resolution to the Middle East conflict.

Crude oil has since rocketed back up above 90 US dollars a barrel as the war shows no sign of ending and the crucial Strait of Hormuz shipping route – through which a fifth of the world’s oil and gas supplies is normally carried – remains closed.

Chancellor John Healey said the Government was taking action to help under-pressure households and the wider economy, but added there was “more to do”.

He said: “Iran war inflation continues to impact prices here at home, but Britain’s economy is resilient.

“We have cut VAT on electricity bills and capped bus fares at £2 – to give breathing space to those feeling the strain.

“There is more to do to restore hope and build a stronger economy.”

The latest data also showed Retail Prices Index (RPI) inflation rose to 3.2% last month from 3% in June – a key figure, with the July rate used to calculate next year’s train fare increase.

Last November, the then-chancellor Rachel Reeves announced that rail fares in England would be frozen in 2026 – the first such freeze for 30 years – but it is unclear if the Government will extend this for a second year.