U.K. Leader Faces Backlash After Market Turmoil

LONDON—Less than a month into her tenure as U.K. prime minister, Liz Truss is seeing her political authority rapidly erode as her bold experiment in British Reaganomics spins out of her control. 

After presenting the biggest tax cuts in a generation to try to jolt the U.K. economy into higher growth, Ms. Truss is locked in a battle on three fronts as she tries to win over skeptical investors, the British people and her own lawmakers. Some in her party are already privately describing her as a lame duck leader, with up to two years before the next general election.