Britons expect a new Prime Minister to be named after Liz Truss quit the position abruptly after only 45 days on the job.
She said her Party will elect a new leader in the next one week.
Tory MPs urged Ms Truss to go after her government was engulfed by political turmoil, following the ditching of most of her economic policies.
Ms Truss was elected by the Tory membership in September, but she lost authority after a series of U-turns.
In a speech outside Downing Street, Ms Truss said the Conservative Party had elected her on a mandate to cut taxes and boost economic growth.
But given the situation, Ms Truss said: “I recognise that I cannot deliver the mandate on which I was elected by the Conservative Party.”
Ms Truss said she would remain in post until a successor formally takes over as party leader and is appointed prime minister by King Charles III.
Jeremy Hunt – who was appointed chancellor last week – has said he will not stand in the leadership contest to be the next prime minister.
In her speech, Ms Truss said she entered “office at a time of great economic and international instability”, as war rages in Ukraine and living costs skyrocket.
But her resignation comes after a key minister, former home secretary Suella Braverman, quit and Tory MPs rebelled in a chaotic parliamentary vote.
Labour leader Sir Keir Starmer called for an immediate general election following Ms Truss’s resignation speech.
