Theresa May must push for a full inquiry into Boris Johnson's burka comments or he will have got away with victimising minorities, the UK's largest Islamic group said today.

The Muslim Council of Britain says Islamophobic incidents have risen since Mr Johnson compared women in veils to bank robbers and letterboxes.

The organisation is today writing to Mrs May today demanding a full disciplinary inquiry as allies including the former Foreign Secretary's father and sister said he 'didn't go far enough'.

The MCB's letter says: 'We are hopeful that the party will not allow any whitewashing of this specific inquiry currently in process. No one should be allowed to victimise minorities with impunity.'

Fiyaz Mughal, the founder of Tell Mama, which measures anti-Muslim incidents, said today that Mr Johnson's comments will 'embolden mainly male perpetrators to have a go at visible Muslim women as a whole'.

Tell Mama says there have been 14 incidents of abuse of women wearing a niqab or hijab in the past week - up from fiev,

Boris Johnson (pictured in his car in Oxfordshire today) sparked controversy after he said that women in burkas look like letterboxes in a column published a week ago

Boris Johnson's father has backed his comments over the burka - but said his son should have called for a ban in 'some circumstances'. Pictured: Boris Johnson and his dad Stanley Johnson

Ban the burka? Women have been outraged by Boris Johnson's comments calling them 'letter boxes' insisting the right to wear the covering clothing should be protected

Mr Mughal said: 'Johnson thinks his flippant comments were funny and whilst his comments were about the burqa, the fact is that visible Muslim women are also impacted on by these comments. Perpetrators don't sit around thinking, 'Oh there is a burqa-clad woman and I will only vent my anger to her' - they see a visibly identifiable woman and off they go with their bigotry and prejudice.'

Boris Johnson's father last night accused the Tory leadership of 'losing its senses' over the burka row embroiling his son.

What did Boris Johnson say about the burqa and the niqab? The ex Foreign Secretary sparked a storm of controversy after using his weekly newspaper column to compare women who wear burqas to letterboxes and bank robbers. The burqa is a full face covering that is associated with a conservative interpretation of Islam. It is different to the hijab, which leaves the face uncovered, or the niqab, which leaves the eyes exposed. In his Daily Telegraph article Mr Johnson said that he felt 'fully entitled' to expect women who wear face coverings to take them off when talking to him at his MP surgery. He also said schools and universities are entitled to take the same approach if a pupil comes in 'looking like a bank robber'. Mr Johnson branded the burqa 'oppressive' and said it is 'weird and bullying to expect people to cover their faces'. He added that he could not find scriptural authority for the dress code in the Koran. And he said 'it is absolutely ridiculous that people should choose to go around looking like letter boxes'. Advertisement

As Cabinet ministers lambasted the party's 'cack-handed' approach, Stanley Johnson claimed Conservative chiefs were 'making a mountain out of a molehill'.

He suggested his son was facing a 'kangaroo court' after describing Muslim women in face-covering veils as looking like letter-boxes or bank robbers.

Rachel Johnson has also backed her sibling.

She wrote: 'If I'd been phoning it in, as it were, I might have changed the word 'ridiculous' and cut out 'bank robbers', but apart from these two or three words, it seemed fine and fair – in fact, it didn't go far enough to express, in my view, how oppressive the garment is.

'When I see a woman wearing one, I don't try to 'other' her. The reverse. I try to imagine myself in her shoes. On the street. All the rest of my family are in casual shorts and T-shirts and flip-flops, but I'm a faceless, unidentifiable ghost in a suffocating black shroud.

'On the beach, my man in skimpy Speedos (OK, please no) me in hot dark fabric from head to toe, having to eat an ice cream by posting the pudding into my mouth from under a flap beneath my chin.'

Ms Johnson also called for her brother to 'go further' saying she would only apologise for his having not called for an outright ban.

The party's treatment of the former foreign secretary – who returned to the UK from holiday in Italy yesterday – has fuelled a Tory civil war.

Conservative chairman Brandon Lewis has called on Boris to apologise for his remarks, made in a newspaper column, while the party is considering formal disciplinary action. However, Mr Johnson's allies believe the ex-London mayor is being targeted because he poses a leadership threat to the Prime Minister.

Tory MP Andrew Bridgen last night said grassroots anger could lead to more MPs submitting letters to reach the 48 needed to force a leadership challenge.

He warned: 'If Boris is suspended it will be open warfare in the Conservative Party. If Theresa May dares engineer a leadership contest while Boris is suspended it will be World War Three.' Yesterday Stanley Johnson told Sky News: 'The hierarchy of the Tory Party has collectively lost its senses. It is making a mountain out of a molehill.

'If ever there was an own goal, the Tory Party is in the process of scoring it with this emphasis on a kangaroo court – it's just nonsense. I blame people who are ready to cook up reasons of their own to attack what was actually a well-written article.'

He accused Labour and Remain-supporting MPs of 'whipping it all up' and insisted: 'We're all making a terrific mountain out of a molehill here.' The Sunday Times reported that four Cabinet ministers had privately expressed dismay at the handling of the case by Downing Street and Tory HQ.

Rachel Johnson and Boris Johnson. Rachel has also backed her brother over his burka comments despite the huge backlash

One minister said: 'It's been so cack-handed. Boris is a backbencher. What he said wasn't that outrageous – a lot of people have said worse and a lot of the party happens to agree with him.

'The sooner the party throws this investigation out, the better. Lots of people both on the front and back benches are really p***** off.' A second minister said: 'It's been a total cock-up from start to finish. What started out as something and nothing has been whipped up into a storm.

'It would have soon blown over, but in their willingness to see Boris punished, all they've done is hurt themselves.' Another added: 'They have managed to engineer a total disaster. There is not a serious political brain in or around Downing Street.

'Trying to silence Boris is stupid, especially when the majority of people agree with him.'

Mr Johnson appeared unfazed by the row as he wore colourful shorts to bring a tray of tea to journalists waiting outside his home in Thame, Oxfordshire.

Meanwhile 53 per cent of voters believe he should not face disciplinary action, according to a ComRes poll for the Sunday Express. Forty per cent said he deserved to be disciplined.

Hamilton is axed over KKK tweet

Former Tory MP's wife Christine Hamilton has been sacked as a charity ambassador after tweeting a Ku Klux Klan photo with the caption: 'If the burka is acceptable then presumably this is too?'

The tweet in the wake of Boris Johnson's burka row sparked fury on social media and Muscular Dystrophy UK severed its links with her. Chief executive Robert Meadowcroft said the decision 'fully reflects the values of the charity'.

This controversial tweet has led to Christine Hamilton's sacking as a charity ambassador

One poster wrote to Mrs Hamilton online: 'You (and Mr Johnson) are both as bad as each other trying to disguise your prejudices as 'jokes'. I hope you're proud of yourself for perpetuating this idea that Muslim women should be vilified and mocked.'

Mrs Hamilton, 68, a former reality show contestant, said the post was 'tongue in cheek', adding: 'For heaven's sake – no, I am not comparing Muslim women to KKK members. I was graphically illustrating how full facial cover can be sinister, which is how many people view the burka.'

Her husband Neil is an ex-Tory MP who is currently the leader of Ukip Wales.