Boris Johnson has stood by his remarks about the burka after the Conservative Party chairman told him to apologise.
The former foreign secretary has been criticised for saying Muslim women wearing burkas “look like letter boxes” and comparing them to “bank robbers”.
PM Theresa May has backed calls for Mr Johnson to apologise, saying the remarks have “clearly caused offence”.
But a source close to Mr Johnson said he “won’t be apologising”, adding it was “ridiculous” to attack his views.
“We must not fall into the trap of shutting down the debate on difficult issues,” the source added.
“We have to call it out. If we fail to speak up for liberal values then we are simply yielding ground to reactionaries and extremists.”
- Johnson burka ‘letter box’ jibe sparks anger
- What’s the difference between a hijab, niqab and burka?
Mr Johnson’s remarks, in a Daily Telegraph article, have provoked criticism from Muslim groups, some Tory MPs and opposition parties.
In the article, Mr Johnson said full-face veils should not be banned but looked “ridiculous”.
However, the founder of the Conservative Muslim Forum said the remarks would harm community relations.
Conservative Party chairman Brandon Lewis said he agreed with Mr Burt that there had been degree of offence in Mr Johnson’s comments, and called on the former London mayor to apologise.
By BBC political correspondent Susana Mendonca
The criticism pitted at Boris Johnson has largely been around the words that he used – “letter boxes” and “bank robbers” to describe Muslim women wearing face veils.
But Mr Johnson hasn’t directly responded to the accusation that it is his language which caused the offence.
Instead, the statement that has come from a source close to him suggests Mr Johnson wants to turn this into a debate about whether or not women should wear the burka at all.
Keeping a high profile is important to Mr Johnson.
He is seen by some in the Conservative Party as a contender for leadership – particularly since his resignation in which he criticised the prime minister’s plan for Brexit.
But he risks being seen as weak if he is forced into an apology by the party chairman.
So his refusal to apologise, and an attempt to now put himself on the side of “liberal values”, could be an example of Mr Johnson trying to save face while maintaining his profile.
Former Conservative chairwoman Baroness Warsi, the first Muslim woman to sit in a British cabinet, welcomed Mr Lewis’s intervention and called for disciplinary action against Mr Johnson if he did not apologise.
She described the remarks as “offensive and deliberately provocative, but very clever politics”.
A debate about the burka should be had “in a serious way”, she said, rather than “trying to get airtime and attention on an issue which he knows will resonate with a certain part of the Tory Party”.
Shazia Awan-Scully, a Muslim who ran as a Conservative candidate in 2010, said she did not agree with wearing the burka but it was up to women to make up their own minds.
She told BBC Radio 4’s PM programme: “Some women choose to wear it, some women are conditioned to wear it, but it’s certainly out of the question for me to tell a woman what to wear.”
She added that the language used by Mr Johnson showed he was “pandering to this Islamaphobic attitude bubbling away in the Conservative Party”, which she said she had experienced herself.
But Conservative backbench MP Andrew Bridgen said Mr Johnson had raised an important subject in a “light-hearted way”.
The reaction “says a lot about internal Conservative Party politics”, he told the BBC.
What is Islamophobia?