London (CNN) UK Prime Minister Theresa May was forced to replace her Defense Secretary on Wednesday as a growing sexual harassment scandal added to the pressure on a government already struggling with the fallout from Brexit.

May named a key Conservative Party fixer, Gavin Williamson, to fill the post vacated after the resignation of Michael Fallon, who admitted his behavior towards women had "fallen short" during his career.

Fallon was the first minister to resign after a swirl of allegations swept British political circles in recent weeks.

Williamson, 41, has been the government's Chief Whip since 2016, in which role he was responsible for enforcing parliamentary discipline within the party.

His rapid elevation to a top Cabinet position has prompted questions in some quarters over his qualifications and whether, in effect he promoted himself, since the chief whip advises the Prime Minister on appointments.

Prime Minister Theresa May faces political tumult over a sexual harassment scandal in Westminster and the torturous Brexit process.

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