She stated that "now feels like the right time to step back," citing her age of 86 and a desire to pursue other activities, including enjoying her garden.
Leith joined the show in 2017 when it moved from the BBC to Channel 4, taking over from Mary Berry as a judge alongside Paul Hollywood.
She expressed her affection for the show and her colleagues, including Paul Hollywood, Alison Hammond, and Noel Fielding.
Former contestants, such as Jasmine Mitchell and Dr Rahul Mandal, have shared their sadness at her departure and praised her impact.