UK borrowing costs have hit levels unseen since before the 2008 global financial crisis, as bond markets deliver their verdict on the country’s political and economic vulnerabilities.
The 10-year gilt yield broke above 5.1% on Monday, its highest since July 2008, as more than 70 Labour MPs called on prime minister Keir Starmer to resign and oil prices surged on renewed Middle East tensions. At the time of writing, 10-year gilts were yielding 5.12%.
The sell-off in gilts has two drivers. Domestically, Starmer is fighting for his political survival following significant Labour losses in the May 2026 local elections, with growing momentum behind a formal leadership challenge.
Globally, Brent crude jumped above $107 a barrel after US president Donald Trump rejected Iran’s ceasefire proposal, reigniting energy-driven inflation fears that cut directly into the UK’s structural weakness as a net energy importer.
The 10-year gilt touched 5.14% at points during Monday morning trading, up roughly 20 basis points over two sessions. The 30-year yield reached approximately 5.75%, near a 28-year high.
The spread between 30-year gilts and equivalent US Treasuries widened from 60 basis points to 78 basis points in just two trading sessions. Markets are now pricing in nearly three additional Bank of England rate hikes before the end of 2026.
Jason Hollands, managing director at Bestinvest, said the move is the product of “a cocktail of mounting geopolitical tensions and domestic political uncertainty”.
“The UK is particularly vulnerable to higher energy prices because it remains heavily reliant on imported energy, meaning any sustained rise in oil and gas costs quickly feeds through into inflation and economic growth concerns,” he added.
That vulnerability is amplified by the energy sector’s weight in UK indices. The sector represents over 11% of the FTSE All Share, Hollands noted, making UK equities especially sensitive to oil and gas price swings.
For bond markets, the worry is what a new leader might do with the public finances. Richard Carter, head of fixed interest research at Quilter Cheviot, said investors are “pricing in a higher risk premium, as speculation around Keir Starmer's leadership and the possibility of a shift towards a looser fiscal stance unsettle confidence in the UK's policy framework”.
Neil Wilson, investor strategist at Saxo UK, said Starmer’s departure now “appears inevitable” and warned that a leftward shift in economic policy would be particularly damaging at this moment.
“A leftwards lurch would raise hackles among bond vigilantes at a time when the fiscal position is already fragile and risks are rising due to rising inflation from soaring energy prices and weaker growth outlook for the economy,” he warned.
Wilson pointed to comments from Louise Haigh, leader of the influential Tribune group of Labour MPs, who called on Tuesday for a reset of the fiscal framework to set longer-term borrowing horizons. “Recalibrating fiscal rules is not the sort of thing the market likes to hear,” he added.
James Lynch, investment manager at Aegon Asset Management, suggested the widening of spreads in the last couple of days is “all political risk” as the market is trying to price in the probability of more gilt-unfriendly policies.
Lynch added that the spread between gilts and other markets can largely be explained by bank rate differentials, meaning “there is more room for underperformance of gilts if it were to price in more political instability”.
In equities, the FTSE 250 fell on Tuesday 1.5% as domestically focused mid-cap stocks bore the brunt. The FTSE 100 was flat, shedding just 0.04%.
Hollands said: “Higher bond yields increase market borrowing costs across the economy and have a knock-on impact on sentiment towards equities, where dividend yields are lower and domestically focused corporates could be hit by weaker consumer spending and higher business costs.”
The path for gilt yields from here depends on three variables: the outcome of the leadership situation at Westminster, the trajectory of energy prices and the Bank of England's response to stickier inflation.
Carter noted that, if Starmer is forced out, any successor will face “very tight constraints”.
“Markets are not passing judgment on ideology so much as arithmetic,” he said. “With debt levels high and global risks already elevated, investors are looking for clarity, discipline and continuity. Without that, the bond market is likely to keep applying pressure, with consequences that are felt well beyond the gilt market itself.”