Britain Wins the Worst Prize: Why the UK Is Taking the Hardest Economic Hit From the Iran War

Of all the unwanted accolades Britain has collected over the years, this one stings. According to the OECD's March 2026 interim economic outlook, the UK faces the steepest growth downgrade of any major economy in the wake of the US-Israel war with Iran. If there were a league table for economic vulnerability, we'd be topping it.

The Grim Figures

The OECD has slashed the UK's 2026 GDP growth forecast to a meagre 0.7%, down from 1.2% in December. That 0.5 percentage point downgrade is the largest of any G7 nation. For context, the eurozone was trimmed by 0.4 percentage points to 0.8%, while the United States actually saw its forecast upgraded by 0.3 points to 2.0%. Life really isn't fair.

On the inflation front, things look even less cheerful. The UK's projection was revised up to 4.0% from 2.5%, a 1.5 percentage point jump that marks the biggest upward revision among major advanced economies. The 2027 outlook offers modest comfort: GDP growth is pencilled in at 1.3% with inflation at 2.6%, still stubbornly above the Bank of England's 2% target.

Why Is Britain Taking the Biggest Punch?

The answer comes down to one word: energy. When the Strait of Hormuz effectively closed on 4 March, roughly 20% of global oil supplies were cut off at source. The United States, sitting comfortably as a net energy exporter, can ride this out. Britain, heavily reliant on imported gas and oil, simply cannot.

The market data paints a vivid picture. Brent crude surged from $81.40 to over $106 per barrel within three weeks, a 30% spike, with some sessions touching near $120. Dutch TTF gas benchmarks nearly doubled, breaching 60 EUR/MWh by mid-March. European gas storage languishes at around 30% capacity after a brutal winter.

For British households and businesses, the pain is already tangible:

• Petrol prices have risen 14p per litre (roughly 10%)
• Diesel is up 29p per litre (about 20%)
• The energy price cap is expected to jump 20%
• Business electricity bills have climbed between 10% and 30%
• Gas contracts in some sectors have spiked by up to 80%
• UK manufacturing costs hit their highest level since 1992 according to PMI data

The Global Fallout

Britain's misery has plenty of company, even if nobody else is hurting quite as badly. Global GDP growth is now projected to ease from 3.3% in 2025 to 2.9% in 2026. The IEA's executive director, Fatih Birol, has described the situation as worse than the 1973 and 1979 oil shocks and the 2022 Ukraine gas crisis combined. That is not a comparison anyone wanted to hear.

The OECD noted that before the conflict erupted on 28 February, the global economy had actually been on track for a 0.3 percentage point upward revision. That optimism has been entirely wiped out.

What Comes Next?

For the UK, previously anticipated Bank of England rate cuts are now firmly off the table. Rate hikes are being discussed instead. Government borrowing costs have jumped by more than 80 basis points, and the OECD has pointed to a double hit from both domestic fiscal tightening and the external energy shock.

The government has responded with emergency measures, including mandatory solar panels and heat pumps in new-build homes. Whether that offers much consolation to anyone filling up their car this week is another matter entirely. Independent forecasters from Barclays, KPMG, Oxford Economics, and Pantheon Macroeconomics broadly corroborate the OECD's gloomy assessment, with estimates ranging from 0.4% to 0.7% growth.

The consensus is clear: buckle up. It's going to be an expensive year.

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