Annual inflation in the U.K. accelerated in July in line with analysts' expectations, official data showed Wednesday, driven primarily by higher household energy bills.

The consumer price index (CPI) rose 2.9% in the 12 months to July, up from 2.6% in June, the Office for National Statistics (ONS) said in a statement.

The rise was spurred by a 13% hike in the price cap on household energy bills that took effect last month, a consequence of the ongoing U.S.-Iran war.

The ONS called it "the largest rise in gas prices for almost four years."

Britain's new prime minister, Andy Burnham, has pledged to ease cost-of-living pressures, unveiling measures such as a tax cut on household electricity prices and a cap on bus fares.

"Iran-war inflation continues to impact prices here at home, but Britain's economy is resilient," Treasury chief John Healey said in response to the latest figures.

"There is more to do to restore hope and build a stronger economy where prosperity is shared more fairly across Britain," he added.

Analysts expect inflation to rise toward the end of the year as higher energy costs feed through to bills further, with little sign of a deal to end the Middle East war.

The Bank of England held its benchmark interest rate at 3.75% last month despite inflation remaining far above its 2% target.

"A renewed spike in inflation has been expected as the war in the Middle East continues to navigate a clunky cease-fire," said Jonathan Raymond, investment manager at Quilter Cheviot.

"Things remain far from normal in the Strait of Hormuz and look unlikely to be resolved any time soon, meaning pressure is likely to remain on prices for the remainder of the year at least," he added.