UK government 30-year gilt demand unexpectedly fell to its lowest level since 2022, highlighting weakening market appetite for long-term government bonds amid rising budget deficits. The declining demand for long-term gilts comes as Chancellor Rachel Reeves continues efforts to convince markets to accept her fiscal spending plans, while concerns persist over the government's £18 billion excess borrowing last month.

The UK Debt Management Office (DMO) sold approximately £1.5 billion of gilts maturing in 2056, attracting £4.6 billion ($6.2 billion) in bids. While this represented more than three times oversubscription, the auction size was unusually small, marking the lowest government bond sale amount in three years. This reduced issuance forms part of the UK government's plan to cut long-term bond offerings, primarily due to waning demand from traditional stable buyers like pension funds amid budget deficit pressures.

Tuesday's results will partially validate the DMO's strategy to reduce debt issuance. Another key measure of gilt demand - the spread between the weighted average accepted price and the lowest accepted price - also weakened significantly beyond expectations. This metric, known as the "tail," widened to 1.4 basis points, up from an already weak 0.8 basis points in a July auction.

The weakening demand for long-term gilts coincides with Chancellor Rachel Reeves' efforts to persuade markets to accept her fiscal proposals. These combined concerns have pushed 30-year UK government bond yields into global focus, with this long-term borrowing cost benchmark touching its highest level this century in early September.

"Investors are very concerned about the fiscal deficit narrative," said Evelyn Gomez-Liechti, senior strategist at Mizuho International Plc, referring to the government's £18 billion above-target borrowing last month.

Following the bond sale, the UK government bond market gave back some of its gains. The 30-year UK government bond yield fell 4 basis points to 5.51%, having dropped more than 5 basis points before the auction.

Despite greater volatility in secondary markets, multiple gilt auctions across various maturities this month have performed relatively steadily overall. Demand for a 10-year UK government bond sale this month even approached record levels.

Excluding upcoming green bond issuances, tap sales, and the Bank of England's quantitative tightening (QT) program, today's gilt sale represents the final long-term gilt offering of the year. Last week, the Bank of England announced it would reduce the proportion of certain long-term UK government bonds sold under its QT program to 20% starting next month, helping to effectively reduce market volatility caused by long-term bond pricing pressures.