Liz Truss left 10 Downing Street with a defiant message that “brighter days lie ahead” as her premiership ended on Tuesday after just seven weeks.
Ms Truss gave a farewell speech in Downing Street before leaving for Buckingham Palace to formally offer her resignation to King Charles III.
She left with a warning that her drive for economic growth could not be postponed forever, even after a vast package of tax cuts blew up her premiership.
“We simply cannot afford to be a low-growth country where the government takes up an increasing share of our national wealth,” she said.
“Our country continues to battle through a storm, but I believe in Britain, I believe in the British people, and I know that brighter days lie ahead.”
Ms Truss leaves after 49 days as the shortest-serving prime minister in British history, breaking the record of George Canning who died after 119 days in 1827.
But she counted a freeze in energy bills and a cut in national insurance — one of the few surviving tax cuts from her aborted package — as achievements of her short tenure.
She said she was honoured to have overseen the mourning period for Queen Elizabeth II, who died on September 8, two days after appointing Ms Truss as her final prime minister.
After eight years in the Cabinet, she said she would return to the backbenches when her successor Rishi Sunak takes office.
Ms Truss was flanked by her husband Hugh O'Leary and her teenage daughters, Frances and Liberty, in her final appearance as prime minister.
Like Boris Johnson before her, she turned to ancient Rome for inspiration in her final speech, quoting the philosopher Seneca: “It is not because things are difficult that we do not dare. It is because we do not dare that they are difficult.”
“From my time as prime minister, I am more convinced than ever we need to be bold and confront the challenges that we face,” she said.
“I wish Rishi Sunak every success, for the good of our country.”
Before offering the king her resignation, Ms Truss chaired her Cabinet for a final time - with some ministers likely to be moved when Mr Sunak takes over.
She told ministers that "in the short time the government had been in place they had secured some significant achievements," Downing Street said.
Liz Truss resigns as prime minister — in pictures
