UK inflation rises by more than expected to 3.5% as war drives up fuel prices

UK annual inflation measures how much consumer prices changed compared with the same month a year earlier. In September, that rate reached 3.5%. This matters because rising inflation reduces the purchasing power of household incomes and can influence interest-rate decisions.

The increase was larger than expected. Inflation had been 3.1% in August, so the annual rate rose by 0.4 percentage points. Economists had forecast a smaller rise to 3.4%. The Office for National Statistics identified petrol and diesel as the single largest factor pushing inflation higher.

Fuel prices rose sharply as oil and gas became more expensive after disruption around the Strait of Hormuz. Petrol increased by 8.2p a litre between August and September 2026, while diesel rose by 10.7p. The rise also reflected weaker-than-usual falls in air fares. Clothing prices fell slightly, while food-price growth remained steady at 1.3%.

The Consumer Prices Index, or CPI, measures the average change in prices of a representative basket of household goods and services. The basket can include food, clothing, transport, energy and other everyday purchases. The annual CPI inflation rate compares today’s basket cost with its cost a year earlier.

Statisticians collect many individual prices and combine them using spending patterns. Items that households spend more on receive greater weight. If petrol prices jump, for example, fuel can make a noticeable contribution to the overall index. The Office for National Statistics uses this process to publish the UK’s inflation rate.

CPI matters because it turns thousands of price changes into one understandable measure. Policymakers use it when judging whether prices are rising too quickly. The Bank of England’s target is 2% inflation. September’s 3.5% rate was therefore substantially above that target, although CPI does not show how every household’s personal costs changed.

Fuel prices rose sharply in September. The average petrol price increased by 8.2p a litre between August and September 2026. Diesel rose by 10.7p a litre. Diesel had already reached a record high of more than £2 a litre that month before easing slightly, while petrol prices climbed above £1.70.

These increases were large enough to make petrol and diesel the biggest single contributor to September’s inflation rise. They also exceeded the changes seen in the same month a year earlier, when petrol fell by 0.2p and diesel fell by 0.4p. Higher fuel costs affect household budgets directly and raise business costs indirectly.

Overall UK inflation reached 3.5%, compared with the Bank of England’s 2% target. That is 1.5 percentage points above target. Officials were also concerned inflation could rise above 4% next year, roughly double the target, as energy costs spread into transport, heating and other goods.

The Strait of Hormuz is a major sea route for fossil fuels. When conflict effectively closed it to most oil and gas traffic, fewer supplies could move through the route. Markets reacted by placing a higher value on available fuel, pushing up prices. The article links this disruption to the war launched by the US and Israel against Iran.

Brent crude rose well above $100 a barrel and was hovering around $110. Higher crude prices increase the cost of producing and supplying petrol and diesel. Gas prices also soared. Diesel was especially affected because it is often refined in the Middle East, making disruption in that region particularly important for supply.

The effect reached UK consumers quickly. Petrol rose above £1.70 a litre, while diesel exceeded £2 before easing slightly. The Office for National Statistics identified petrol and diesel as September’s largest inflation driver. Continued disruption could also raise transport, heating and wider business costs.

Fuel prices affect much more than motorists. Lorries, trains, ships and aircraft use energy to move people and goods. Businesses also use fuel or gas for production, storage, heating and delivery. When energy becomes more expensive, their operating costs rise. That can reduce profits or lead firms to charge customers more.

The article gives air fares as an immediate example. They fell in September, but by much less than usual after the summer peak because aviation fuel costs were higher. Food can also become more expensive when farms, food processors, warehouses and supermarkets face higher transport and energy bills. Heating costs rise directly when household energy prices respond to gas markets.

This process is called cost-push inflation: a supply shock raises business costs and then consumer prices. The article warns that higher commercial transport and domestic heating costs could lift inflation above 4% next year. Food-price growth was still 1.3% in September, partly because supermarket competition offset transport increases.

The Bank of England raises interest rates to cool demand when inflation is too high. Higher rates increase the cost of mortgages, loans and business borrowing. They can also encourage saving. With less money being spent, companies may find it harder to raise prices and workers may face less pressure for large pay increases.

Rates cannot repair a damaged fuel supply. The article’s Martin Beck makes that point directly: higher rates cannot produce more oil or gas. However, policymakers worry that an energy shock could spread into transport, food, heating and other prices. Tighter financial conditions can limit that second-round effect and help keep inflation expectations under control.

The trade-off is weaker economic growth. Beck warned that further tightening could weaken an already fragile economy. Even so, he said a rate increase on 5 November looked increasingly likely. Investors were pricing in four hikes over the following year, although an improved international climate could quickly change the outlook.

The article does not set out alternative routes or policies, so the following are established energy-policy options rather than claims from the source. The UK could diversify imports through other shipping routes and suppliers, reducing dependence on any single chokepoint. It could also maintain larger fuel and gas reserves to cushion short disruptions.

Longer term, expanding offshore wind, nuclear power, solar generation and electricity networks could reduce reliance on imported fossil fuels. Better home insulation, efficient heating systems and lower-energy transport would reduce demand. Electrifying cars, buses and some industrial processes could also limit exposure to oil-price shocks, provided reliable low-carbon electricity is available.

Policy could support these changes through grid investment, planning reform, targeted household grants and emergency fuel measures. Domestic production may add resilience, but it would not instantly replace disrupted imports. The article’s immediate warning remains that higher oil and gas prices can raise transport, heating and other costs, while the government has limited room because borrowing costs are high.