OBR Warns Iran Conflict Could Deliver ‘Significant’ Hit to UK Economy as Gilt Yields Spike
The fiscal watchdog flagged Middle East tensions as a key risk to its forecasts as 10-year gilt yields jumped to 4.30% amid renewed inflation fears and energy market turmoil.
The Office for Budget Responsibility warned Tuesday that conflict in Iran could deliver significant impacts to the UK economy, particularly through energy markets, as gilt yields rose and investors trimmed expectations for near-term interest rate cuts.
Chancellor Rachel Reeves delivered her Spring Statement against a backdrop of escalating geopolitical risk, with the OBR noting that conflict in the Middle East could have “significant impacts on the global economy, particularly Energy Markets.” The warning comes as UK 10-year gilt yields surged to 4.30%, rebounding from a one-year low, as escalating Middle East tensions unsettled global markets and led traders to scale back expectations for interest rate cuts. The timing underscores how quickly geopolitical shocks can reshape fiscal arithmetic: the OBR’s forecasts indicated GDP growth of 1.1% in 2026, down from the 1.4% forecast in November, though the projection was drawn up before the war in Iran and may already be out of date.
Energy Shock Transmission Channels
The economic transmission mechanism runs through multiple channels. Brent crude jumped as much as 13% on the strikes, to around $82 a barrel, on fears of supply disruption. More concerning for UK households, UK gas futures contracts for month-ahead delivery jumped nearly 20% to 135.5p per therm, following a 40% surge on Monday. The Strait of Hormuz—through which roughly 20 percent of global petroleum and liquefied natural gas is shipped—has become the critical chokepoint, with insurers temporarily halting coverage for vessels transiting the waterway.
According to Oxford Economics, a moderate disruption in the Strait of Hormuz would only knock 0.1 percentage point off world GDP growth this year, with a moderate disruption potentially pushing the average oil price to almost $80 per barrel in Q2 before gradually falling back. However, US and Eurozone CPI inflation would only average 0.3–0.4 percentage points more in 2026, which will do little to crimp spending and is unlikely to prompt central banks to contemplate a significant change to their courses for policy rates.
The OBR’s forecasts were finalized before the weekend US-Israeli strikes on Iran that reportedly killed Supreme Leader Ayatollah Khamenei. Markets now face the question of whether maritime traffic through the Strait of Hormuz resumes within days or remains suspended for months—a distinction that will determine whether this becomes a transitory price spike or a sustained inflationary shock comparable to 2022.
Fiscal Space Under Pressure
The gilt market response reveals how quickly geopolitical risk can erode fiscal headroom. Ten-year yields rose by five basis points to 4.28%, a modest move that nonetheless underscored investor caution, as lower gilt yields since November had provided welcome relief for the Treasury. More dramatically, UK 10-year gilt yields surged to 4.4%, their highest level since February 13, with natural gas and crude oil prices jumping following the formal closure of the Strait of Hormuz and the ongoing suspension of Qatari LNG exports, heightening the risk of prolonged energy-driven inflation.
The Chancellor emphasized stability in her statement, but markets are listening less to what is happening in the House of Commons and more on the war in the Middle East, with expectations that higher oil prices will flow through to re-inflation sending yields higher and cooling expectations for interest rate cuts. According to Retail Banker International, the market is now struggling to price in even a quarter point cut from the Bank of England’s Monetary Policy Committee.
The fiscal arithmetic is unforgiving. The OBR now expects fiscal headroom to be £23.6 billion by the end of the forecast period (2029/30). But any sustained rise in yields would narrow the Chancellor’s fiscal headroom, potentially forcing difficult choices between tax rises, spending cuts, or relaxing fiscal rules—all politically toxic options for a government already facing public discontent.
| Year | November Forecast | March Forecast |
|---|---|---|
| 2026 | 1.4% | 1.1% |
| 2027 | 1.5% | 1.6% |
| 2028 | 1.5% | 1.6% |
| 2029 | 1.5% | 1.5% |
Inflation and Interest Rate Calculus Shifts
The conflict has upended the disinflationary narrative that underpinned expectations for monetary easing. Traders have slashed bets that the Bank of England will cut UK borrowing costs at its meeting later this month, with money markets now believing Threadneedle Street has a 29% chance of reducing rates from 3.75%, down from around 80% last week. The shift reflects concerns that energy-driven inflation could prove stickier than anticipated.
According to Yahoo Finance UK, higher energy costs—not just at petrol pumps but also heating bills, production costs, everything regarding transport and more—have an inflationary impact. The RAC warned that oil prices reaching 100 dollars per barrel would take petrol prices “nearer to 150p per litre,” up from recent lows of 131.9p.
The European Central Bank’s chief economist Philip Lane told the Financial Times that “directionally, a jump in energy prices puts upward pressure on inflation, especially in the near term.” The analysis suggests central banks face a renewed dilemma: tighten policy to contain inflation, or ease to support growth as energy shocks weigh on activity.
“With the unfolding conflict in Iran and the Middle East, it is incumbent on me and on this government to chart a course through that uncertainty, to secure our economy against shocks and protect families from the turbulence that we see beyond our borders.”
— Rachel Reeves, UK Chancellor of the Exchequer
Scenario Modeling and Tail Risks
Economic models suggest the impact depends critically on duration. Oxford Economics outlined scenarios ranging from controlled escalation to prolonged disruption. In a moderate scenario where tit-for-tat attacks continue and Iranian oil exports cease, there would be a 4% reduction in global oil supply, with Brent likely settling closer to $90 per barrel through 2026, and global growth would take a mild hit with models suggesting a 0.2 percentage point downgrade to global GDP.
The tail risk involves sustained Strait of Hormuz closure. Quantitative extrapolation from 1990–91 Gulf War data, scaled to current inventory buffers, projects oil prices above $100 per barrel for 60+ days, translating to global recession risks of 1.0–1.8% GDP contraction in net-importing economies. For the UK specifically, the possible closure of the Strait of Hormuz due to conflict in the region may cause a decline in global GDP of 0.8%.
The Atlantic Council noted that what will determine the economic pressure is whether maritime traffic through the Strait of Hormuz resumes within days or remains suspended for months. So far, regional infrastructure remains intact and supply has not been structurally impaired, with oil-market fundamentals prior to Operation Epic Fury supporting supply outpacing demand in 2026.
- Direct energy price shock: Brent crude up 13%, UK gas futures up 20% in single session
- Borrowing cost pressure: 10-year gilt yields at 4.30%, eroding £23.6bn fiscal headroom
- Interest rate expectations: BoE March cut probability collapsed from 80% to 29%
- Supply chain disruption: 20% of global oil and gas flows through Strait of Hormuz
- Inflation persistence: Energy-driven CPI pressures threaten 2% target timeline
What to Watch
The next fortnight will determine whether this becomes a transitory shock or structural shift. Key indicators include daily vessel counts through the Strait of Hormuz, insurance premium movements for Gulf shipping, and whether oil inventories in consuming nations begin drawing down rapidly. For UK policymakers, the March 20 Bank of England meeting now carries heightened significance: a hold would signal inflation concerns trump growth support, potentially validating market repricing of the rate path.
Gilt market behavior will reveal whether investors view the OBR’s £23.6bn headroom as adequate buffer or prelude to fiscal slippage. Should 10-year yields breach 4.50% on sustained basis, pressure will mount on Reeves to announce offsetting measures in the autumn Budget. The Chancellor faces a narrow path: maintain fiscal credibility to anchor gilt yields while avoiding pro-cyclical tightening that could tip a fragile recovery into contraction. The iron law of open-economy macroeconomics—that small countries cannot control both their exchange rate and monetary policy in a crisis—may soon apply to Fiscal Policy as well. Markets, not ministers, increasingly set the terms.