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Long-term UK borrowing costs rise to highest since 1998, sterling slumps as Starmer’s future in doubt

By Thomson Reuters May 12, 2026 | 2:39 AM

By Yoruk Bahceli

LONDON, May 12 (Reuters) – Long-dated UK borrowing costs surged to their highest in nearly 30 years, sterling slumped and shares fell on Tuesday as investors brace for a potential change ​of leadership that could weaken fiscal discipline.

Keir Starmer was consulting colleagues ‌about whether he can stay on as Britain’s prime minister on Tuesday, ahead of a crunch cabinet meeting at 0830 GMT that comes after ministerial aides quit and almost 80 lawmakers publicly called for him to go following a last week’s big defeat ‌in ​local elections.

Investors are worried that a replacement would ⁠be more left-wing than Starmer ⁠and push for more spending at a time when Britain’s finances are already stretched.

UK borrowing costs remain the highest among the Group of Seven advanced economies and have risen the most since the Iran war, ​so a further rise will add to the pressure on its public finances.

The benchmark 10-year gilt yield jumped 11 basis points (bps) to 5.11%, just ⁠below the highest levels since 2008 it ⁠hit in March on concerns around the inflationary impact of ​the Iran war.

Longer-dated 20 and 30-year yields, more sensitive to fiscal risks, rose ​to their highest since 1998, at 5.12% and 5.80%.

“The bond ‌market is reacting not only to Starmer’s potential departure, but also to who his successor could be, and to the prospect of a drawn-out leadership battle that leads to more fiscal promises that the UK cannot afford,” said ⁠Kathleen Brooks, research director at broker XTB.

The pound dropped 0.7% to $1.351 and was 0.4% lower against the euro at 86.92 pence .

Stock markets also came under pressure ⁠with the FTSE 100 ‌index down 0.5% .

British banks also fell with Barclays dropping ⁠4%, while Natwest and Lloyds fell over 3% each .

British ​banks were ‌leading declines among European banking stocks.

Analysts at JPMorgan said ​they now ⁠expected Britain’s banking surcharge to rise to 5% from 3% as a leftward shift in policy is more likely.

Bond markets were also under pressure across Europe as hopes for a peace deal on Iran faded on Tuesday as U.S. President Donald Trump said a ceasefire was on “life support”.

(Reporting by Yoruk Bahceli; editing ​by Dhara Ranasinghe)