Defense Secretary Michael Fallon has resigned after admitting his behavior in the past may have "fallen short." He is the first minister to step down from PM Theresa May’s government in the growing sexual harassment scandal at Westminster.

In his resignation letter to May, Fallon wrote: “A number of allegations have surfaced about MPs in recent days, including some about my previous conduct. Many of these have been false, but I accept that in the past I have fallen below the high standards that we require of the Armed Forces that I have the honor to represent. I have reflected on my position and I am therefore resigning as Defence Secretary.”

Fallon added that he would still work hard as an MP for his Sevenoaks constituents, and that it had been a “privilege” to have been defense secretary over the last three and a half years.

Michael Fallon's resignation letter pic.twitter.com/iJJ61QRFXh — Archie Bland (@archiebland) November 1, 2017

In a written reply to Fallon, the prime minister said she appreciated the “characteristically serious manner” in which Fallon considered his position. She praised his “diligent service.”

May will now have to carry out a cabinet reshuffle with tense Brexit negotiations due to resume next week in Brussels.

May's letter responding to Fallon pic.twitter.com/NLucp4ROAJ — Archie Bland (@archiebland) November 1, 2017

Earlier this week, Fallon admitted to inappropriately touching a female journalist. He insisted that he apologized over the incident 15 years ago, however, and that he and the journalist considered the matter closed. The journalist, Julia Hartley-Brewer, previously disclosed the incident but did not name Fallon. She said that at the time she had threatened to punch him in the nose if he did it again.

Unlike other incidents outlined in the so-called “dirty dossier” circulating at Westminster, the Prime Minister did not refer Fallon for a Cabinet investigation.

According to the Telegraph, there will not be a Cabinet reshuffle, but Fallon will be directly replaced.

Some 40 Tory MPs have been named in the dossier, which was compiled by Conservative Party staff about politicians against whom accusations of misconduct have been made.

Fallon is the first minister to step down from May's government in the growing scandal about sexual harassment at Westminster. Other allegations have emerged about ministers in recent days, including the first secretary of state, Damian Green, who has been accused of making inappropriate advances towards activist Kate Maltby.