The prime minister believes expletive-laden text messages sent by Sir Gavin Williamson to a colleague are “unacceptable”, No 10 has said.
A series of messages sent by Sir Gavin to ex-chief whip Wendy Morton were published on Sunday.
Downing Street confirmed the prime minister knew about a complaint against Sir Gavin before appointing him to cabinet, but had not seen the messages.
Opposition parties have said Sir Gavin was not fit to be a minister.
The Sunday Times published texts said to have been sent by Sir Gavin to Ms Morton in which he accused her of excluding some MPs from the Queen’s funeral.