(Bloomberg) -- Boris Johnson, the U.K.’s former foreign secretary, is to be investigated by the Conservative Party after he ridiculed Muslim women who wear burqas, saying they look like “letter boxes” and “bank robbers.”

The party received a series of complaints about the former mayor of London, who quit May’s cabinet last month in protest at her Brexit policy, and an independent panel will decide whether he has broken the party’s code of conduct, an official said.

In a column for the Daily Telegraph newspaper on Monday, Johnson argued against a ban on the burqa, while saying people who wear the garment look “ridiculous.” He’s remained silent since then, in the face of calls from Prime Minister Theresa May and Conservative Party Chairman Brandon Lewis to apologize.

“It’s very clear that that language that Boris used has offended people,” May said on Tuesday.

To contact the reporter on this story: Thomas Penny in London at tpenny@bloomberg.net

To contact the editors responsible for this story: Flavia Krause-Jackson at fjackson@bloomberg.net, Alex Morales

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