UK government bonds fell sharply after Manchester Mayor Andy Burnham opened a route to challenge Keir Starmer for the prime minister's job. The move spooked fixed-income markets, with traders pricing in elevated political risk and potential fiscal expansion under a less orthodox Labour leadership.

Gilts dropped as investors weighed the implications of a contested leadership contest within the ruling party. A challenge to Starmer's authority would inject fresh uncertainty into Westminster, raising concerns about policy continuity and the pace of deficit reduction. Bond yields climbed as the market reassessed the probability of looser spending commitments.

For businesses and households, higher borrowing costs could follow if fiscal discipline weakens. The Labour government's fiscal strategy depends heavily on political cohesion, and a leadership fight would complicate that. Investors read the political instability as a catalyst for more expansive government spending.