Home Secretary Amber Rudd has resigned, Downing Street has said.
Ms Rudd, who was due to make a Commons statement on Monday, was under pressure to quit over the Windrush scandal.
She has faced criticism over the existence of Home Office removals targets and her knowledge of them.
On Sunday, the Guardian published a letter to Theresa May, in which Ms Rudd set out her "ambitious but deliverable" aim to deport 10% more illegal immigrants over the "next few years."
Ms Rudd telephoned the prime minister on Sunday evening to tell her of the decision amid intensifying opposition demands for her to quit.
A No 10 spokesman said: "The Prime Minister has tonight accepted the resignation of the Home Secretary."