The cost of UK government borrowing climbed to its highest level in nearly two decades on Tuesday, as mounting speculation over the future of Prime Minister Sir Keir Starmer collided with fresh inflation fears stoked by the Iran conflict, leaving the country’s small and mid-sized businesses staring down the barrel of yet another period of squeezed credit and weaker sterling.
The effective interest rate on 10-year gilts briefly touched 5.13% in morning trading, a level not seen since the depths of the 2008 global financial crisis. Yields on two-, five- and 30-year debt also pushed higher, with the 30-year benchmark hitting 5.80% — the steepest reading since 1998.
For Britain’s 5.5 million SMEs, already grappling with stubborn input costs and a softening consumer, the move in the bond market is no abstract Westminster drama. The two- and five-year gilt yields directly underpin fixed-rate mortgage pricing, and by extension the working capital pressures on owner-managers whose households and balance sheets remain tightly interwoven.
The FTSE 100 slid 0.5%, with the high-street banks leading the retreat amid chatter that any successor administration could green-light a fresh tax raid on the sector. Sterling weakened by the same margin against the dollar, slipping to $1.35.
A toxic cocktail of geopolitics and Westminster jitters
Markets have been on edge for weeks as the war in Iran has driven crude above $100 a barrel, threatening to reignite the very inflationary fire the Bank of England has spent two years dousing. But while peer economies have weathered the oil shock with comparatively muted moves in their debt markets, Britain’s gilts have been singled out for punishment.
The reason, according to City analysts, is political. With Sir Keir’s grip on Number 10 looking increasingly precarious, allies emerged from a cabinet meeting on Tuesday insisting the Prime Minister would “get on with governing”, investors are pricing in the very real prospect of a leadership contest that could deliver a Chancellor less wedded to fiscal restraint.
Sir Keir and Chancellor Rachel Reeves have spent the better part of a year repeating their commitment to “iron-clad” borrowing rules, a mantra designed to keep the bond vigilantes at bay. Yet a growing chorus of Labour backbenchers on the party’s left have begun openly questioning whether those self-imposed limits are “fit for long-term renewal”.
Capital Economics put the matter bluntly in a note to clients. “The UK’s already fragile fiscal position means that investors will be on edge for any signs of fiscal loosening,” its analysts wrote. “The likely replacements for Starmer/Reeves would probably not be as fiscally disciplined.” The firm flagged Andy Burnham, Angela Rayner and Wes Streeting, the names most frequently cited as potential challengers, as candidates who would “probably raise public spending”.
Why the City is nervous
Anna Macdonald, investment strategy director at Hargreaves Lansdown, said the gilts market had been “frazzled” by the prospect of a new occupant of Number 11 taking a more relaxed view of the public finances. “This would mean that investors, of which 25-30% are overseas buyers of UK government bonds, demand a higher risk premium,” she warned.
That risk premium matters far beyond the trading floors of the Square Mile. Governments raise most of their revenue through taxation, but routinely spend more than the Exchequer takes in. The shortfall is plugged by issuing gilts, IOUs sold to pension funds, insurers and foreign investors who, in exchange for parting with their cash, demand certainty above almost everything else.
When that certainty evaporates, the price of borrowing rises. And the bill for Britain’s existing stock of public debt, already swollen by years of crisis-era spending — now accounts for roughly £1 in every £10 the government spends. Each tick higher in yields translates directly into less fiscal headroom for the productivity-boosting investment SMEs have been calling for, from full-expensing reforms to business rates overhaul.
For owner-managers, the immediate read-through is threefold. Mortgage rates, already a drag on consumer discretionary spend, are likely to remain stickier for longer. Sterling weakness will sharpen the import bill for any business reliant on dollar-priced inputs, from manufacturers to hospitality operators sourcing food and drink from overseas. And the cost of business borrowing, whether through term loans or asset finance, is unlikely to ease until the bond market regains its composure.
Until Westminster offers a clearer answer to the question of who will be running the country by the autumn, that composure looks some way off.
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Uk borrowing costs spike to 18-year high as Starmer leadership crisis spooks markets