Hate crimes against Muslim women in Britain could jump after former Foreign Minister Boris Johnson likened burqa-wearers to "letter boxes" and "bank robbers," activists said on Thursday.

Anti-hate crime groups said the comments by Johnson, who resigned last month, would encourage Islamophobic and sexist abuse at a time when attacks were already on the rise. "This inflammatory language will in fact motivate and fuel hate crimes, particularly towards visibly Muslim women who wear the veil or the hijab," Sajda Mughal, who runs the JAN Trust charity, told the Thomson Reuters Foundation. She said that her group, which works with marginalized women, had already taken three calls in the last two days from hijab-wearing women who reported being called "letter boxes."

A top Conservative known for flamboyant phrasing and eccentric stunts, Johnson is facing an internal Conservative investigation over his remarks, which have reignited a debate over religious facial coverings and split his party. Some 100 Muslim women who wear the niqab or burqa have written to Brandon Lewis, chairman of the Conservative Party, demanding that Boris Johnson be kicked out of the party. The letter, revealed by Sky News, says that an apology by the former foreign secretary would be insufficient and that more should be done to prevent others in the party from following suit.

"We speak as free women who are able to speak for ourselves and make our own choices," the signers said, as reported by Anadolu Agency (AA).

The Muslim Council of Britain (MCB) has welcomed the Conservative Party decision to launch an inquiry into the former foreign secretary over his recent Islamophobic remarks, a statement said Thursday.

"We welcome the steps the Conservative Party has taken, but the road ahead is long. While the choice of panelists is for the Party to decide, to avoid accusations of a whitewash, the group should include people who are aware of the seriousness of the issue and its effect on society," said Harun Khan, secretary general of the MCB. "Any investigation looking into Mr. Johnson's incendiary comments must take into account the impact on the victims, in this case, Muslim women," he added.