LONDON — Former British foreign secretary Boris Johnson faces an investigation by an independent panel over complaints that he violated the ruling Conservative Party’s code of conduct when he wrote in a newspaper column last week that women in burkas resemble ‘‘bank robbers’’ and ‘‘letter boxes.’’

Johnson resigned as Britain’s top diplomat a month ago after claiming that Prime Minister Theresa May’s proposals for a soft exit from the European Union were killing the dream of a clear, decisive split from the bloc.

Johnson remains a backbench member of Parliament and contender to replace May in a future contest for power. After quitting his Cabinet post, the flamboyant former London mayor took up his pen as a paid opinion writer for the Daily Telegraph.

His most recent column noted his opposition to a new ban on face veils in Denmark but veered away to critique traditional Islamic garb, calling niqabs and burkas ‘‘oppressive and ridiculous.’’

Johnson asserted that schools should be entitled to tell students to remove a veil if one ‘‘turns up . . . looking like a bank robber.’’

Johnson was called upon to apologize but declined, according to his employers.

He is believed to be on vacation.

About 5 percent of the British population is Muslim.

washington post