If she was appointed, Dame Antonia would be the first female head of the Civil Service.
Critics of the Downing Street operation, including Culture Secretary Lisa Nandy, have claimed there has been a “boys’ club” culture and called for more women to be given senior roles.
Given the job just over a year ago, Sir Chris looks set to become the shortest-serving cabinet secretary in the history of the post.
At the time of his appointment, the PM said Sir Chris would be tasked with “the complete re-wiring of the British state to deliver bold and ambitious long-term reform”.
However, as a career civil servant some questioned whether he was the best person to reform the Civil Service and reports that Downing Street was unhappy with his performance in the role have swirled for months.
Sir Chris also had ultimate responsibility for the due diligence checks carried out before Lord Mandelson’s appointment, although he took up the role only a few days before the appointment was formally announced.
He would be the latest senior official to leave the government operation in the last week, following Sir Keir’s chief of staff Morgan McSweeney and his director of communications Tim Allan, as the PM seeks to reset his team following the Mandelson scandal.