Nick Clegg has said he will not drop a Liberal Democrat parliamentary candidate who sparked widespread protests among some Muslims by tweeting a cartoon of the prophet Mohammed.
Maajid Nawaz says he has received death threats since posting the image earlier this month, while a petition calling for him to be ditched as Lib Dem candidate for Hampstead and Kilburn in next year's general election has gathered more than 20,000 signatures, and a rival petition in his defence has more than 7,000.
Mr Clegg told LBC 97.3 radio that he would not personally have tweeted the controversial cartoon - which shows a stick figure of Jesus saying "Hi" to a stick figure called Mo, who replies "How you doin'?" - and said it was important to show "respect" to people of all faiths and none when discussing religious matters.
But the Lib Dem leader said: "He is not going to be dropped as a Liberal Democrat candidate. He has the right - as any Muslim, non-Muslim or anyone of any faith or none in this country has - to say things even if that causes offence to other people.
"It so happens that what he did does cause real offence to many, many Muslims in this country. All I would say is that we have to make sure that that debate, sensitive though it is, is conducted in a respectful way in moderate terms.
"I would not have tweeted that thing, clearly. I will defend anyone's right to deploy the freedom of expression in this country. I'm not going to start censoring people in a free society."
Mr Nawaz, the co-founder of counter-extremism think-tank the Quilliam Foundation, posted the image after appearing in a BBC television debate about religious tolerance which featured two students wearing it on T-shirts.
He said that he was sending out the "bland" cartoon to show that, as a Muslim, he did not feel it was a threat to his faith and to demonstrate that "Muslims are able to see things we don't like, yet remain calm and pluralist".
"My intention was not to speak for any Muslim but myself - rather, it was to defend my religion from those who have hijacked it just because they shout the loudest," Mr Nawaz has said.
"My intention was to carve out a space to be heard without constantly fearing the blasphemy charge, on pain of death."
Speaking on his LBC Call Clegg show, Mr Clegg said: "I know how very strongly people feel about this. The cartoon and subsequent debate has caused a lot of offence to many Muslims across the country.
"But we simply cannot tolerate anyone in a free country - where we have to protect free speech, even if that free speech might cause offence to others - being subject to death threats and them and their family being put under extraordinary pressure to recant what they said.
"Having said that, I would be the first to say that when you are dealing with issues of religion and deeply held faith, you have got to express yourself moderately and sensitively and with respect one to the other.
"That is the corollary of freedom of speech, it is also the freedom to deploy that freedom of speech in a sensitive and moderate way. That's why Maajid has been right to express and acknowledge regret at some of the ways he has responded in the debate."