Boris Johnson is to face investigation by an independent panel following complaints that his comments on the burka breached the Conservative Party’s code of conduct.
It is understood that the process is being triggered automatically after the receipt of a number of complaints over the former foreign secretary’s comparison of Muslim women in face-covering veils with bank robbers or letter boxes.
The party declined to comment on the disciplinary procedure.
A spokesman said only: “The code of conduct process is strictly confidential.”
But party rules state that formal complaints against Conservative representatives will be investigated “in a timely and confidential manner” by someone “with appropriate experience and no prior involvement in the complaint”.
“The investigation should be thorough, impartial and objective, and carried out with sensitivity and due respect for the rights of all parties concerned,” says the code of conduct.
News of the investigation emerged as Mr Johnson was reprimanded for breaching rules for former ministers by failing to seek advice before taking up a job as a newspaper columnist after leaving the Cabinet.
The Advisory Committee on Business Appointments (Acoba) said it was “unacceptable” that he signed a contract with the Daily Telegraph on July 12 - three days after quitting as foreign secretary - but did not ask for its advice on the propriety of the move until 14 days later, by which time his appointment was public knowledge.
This was “a failure to comply with your duty” under the Government’s business appointment rules for former ministers, Acoba told Mr Johnson.
It was in his weekly Telegraph column that Mr Johnson made comments which sparked demands for an apology from a host of figures from all sides of politics, including Theresa May, Tory chairman Brandon Lewis and Scottish Conservative leader Ruth Davidson.
The founder of the Conservative Muslim Forum, Lord Sheikh, was one of those to write to Mr Lewis to demand “serious action” in response to what critics described as Islamophobia by the former Cabinet minister.
Mr Johnson, who is holidaying abroad, has made no response to demands for an apology.
And there was no immediate comment on the news that he faces investigation.