The minister for small business, Andrew Griffiths, has resigned from the government after sending text messages of a sexual nature to two female constituents.
The contents of the texts will be revealed in the Sunday Mirror.
Mr Griffiths, MP for Burton and Theresa May’s former chief of staff, told the Mirror he was “deeply ashamed”.
His behaviour had caused “untold distress” to his wife and family to whom he “owed everything”, he said.
He also apologised for the “deep embarrassment” caused to the prime minister and the government, in a statement made to the newspaper.
He added that he has referred himself to the Conservative Party’s Code of Conduct procedures following discussions with the chief whip.
BBC political correspondent Iain Watson said Mr Griffiths, who decided to resign on Friday night, “jumped before he was pushed”.
The text messages were understood to be very damaging and contained offensive language, our correspondent added.
Mr Griffiths, an MP since 2010, is very well known to the prime minister having been her chief of staff in opposition.
He became a father in April when his wife gave birth to a baby girl.