THERESA May faces a surge in letters calling for a no-confidence vote if Boris Johnson is hauled over the coals for his burka jibes.

Furious Tory backbenchers made the warning as the ex-Foreign Secretary’s family rushed to his defence.

The party’s influential 1922 backbench committee needs just 48 letters to trigger a no-confidence vote in the PM — and MPs believe 38 have already been sent in the wake of her soft Chequers Brexit plan.

The Sun on Saturday revealed Mr Johnson could be sent for diversity training. But one MP said: “Any punishment beating will be the tipping point.

"People will send letters in. They can’t believe what’s happening.”

The fresh backlash came a week after BoJo wrote in a newspaper column that women wearing burkas look like letterboxes or bank robbers.

Yesterday Mr Johnson’s Lib Dem sister Rachel said he had been wrong to use the term “bank robbers” — but that he should have called for an outright ban.

Their father Stanley he should have gone further and talked about Sharia Law and banning halal food.

President Trump’s former strategist Steve Bannon urged Mr Johnson not to “bow at the altar of political correctness” by apologising.

The Muslim Council of Britain is writing to Theresa May to demand Boris Johnson face a full disciplinary inquiry. It said it was vital the Tory party wouldn’t allow any “whitewashing.”