(CNN) Italian fashion designer Stefano Gabbana and Elton John are in a war of words on social media, calling for boycotts of each other's work.

The argument stems from comments about in-vitro fertilization in Panorama magazine, in which Gabbana and longtime collaborator Domenico Dolce spoke about "synthetic" children born from "rented" wombs.

"No chemical children: life has a natural course, there are things that shouldn't be modified," the magazine says in a quote attributed to both designers. The magazine also promises insights from the designers on "the importance of relationships within conventional families with very, very traditional values" in an interview that hit Italian newsstands last week.

John, who has two children with husband David Furnish through IVF, issued a strong repudiation of the statements on Sunday and pledged to boycott the Dolce & Gabbana fashion line.

In response, Gabbana defended his " freedom to speak " and called on fans to boycott John.

JUST WATCHED Elton John leading Dolce & Gabbana boycott Replay More Videos ... MUST WATCH Elton John leading Dolce & Gabbana boycott 03:25

Sir Elton appears to be winning the social media war with the hashtag #BoycottDolceGabbana, which by Monday morning had been used more than 35,000 times on Twitter since John invoked it on Sunday. By comparison, Gabbana's #boycotteltonjohn has been used just 1,600 times on Twitter, according to social media search tool Topsy.

"How dare you refer to my beautiful children as 'synthetic'. And shame on you for wagging your judgemental little fingers at IVF - a miracle that has allowed legions of loving people, both straight and gay, to fulfill their dream of having children," John said Sunday on Instagram.

"Your archaic thinking is out of step with the times, just like your fashions. I shall never wear Dolce and Gabbana ever again."

How dare you refer to my beautiful children as "synthetic". And shame on you for wagging your judgemental little fingers at IVF - a miracle that has allowed legions of loving people, both straight and gay, to fulfil their dream of having children. Your archaic thinking is out of step with the times, just like your fashions. I shall never wear Dolce and Gabbana ever again. #BoycottDolceGabbana A photo posted by Elton John (@eltonjohn) on Mar 14, 2015 at 10:29pm PDT

The sentiment quickly gathered support from such celebrities as Ricky Martin, Al Roker and Courtney Love. Tennis star Martina Navratilova tweeted her support for John's post, saying "My D&G shirts are going in the bin — don't want ANYONE to wear them."

.@dolcegabbana ur voices R 2powerfull 2B spreading so much h8 http://t.co/30Oe2hcxNt Wake up,Its 2015 Luv urselves guys #boycottdolcegabbana — Ricky Martin (@ricky_martin) March 15, 2015

In spite of what @dolcegabbana think, my beautiful IVF children are not "synthetic children". I agree with @eltonjohndotcom — Al Roker (@alroker) March 15, 2015

Parents and IVF advocates also joined the boycott.

"My son is NOT synthetic. His life was made possible through #IVF & I couldn't be more grateful," writer and infertility advocate Jenn Palumbo said in a tweet

My son is NOT synthetic. His life was made possible through #IVF & I couldn't be more grateful. #BoycottDolceGabbana pic.twitter.com/ia347woYCg — Jenn (Jay) Palumbo (@jennpal) March 16, 2015

The comments from Dolce and Gabbana struck some as hypocritical coming from a couple that was romantically involved until 2005 (they continued working together after the breakup). Still, Gabbana has dropped hints in interviews of his "traditional" views toward family structure. He told an Italian publication in 2006 that he once asked a female friend to be a surrogate mother because he was "opposed to the idea of a child growing up with two gay parents."

Gabbana was quick to react to this controversy, calling John a "fascist" in an Instagram comment that was later deleted, according to CNN affiliate TGCom24 . He also sought to discredit reports that they told Panorama in this instance they objected to same-sex adoption, even though Gabbana took that position in his 2006 interview

By Sunday evening, Gabbana's Instagram feed was full of screengrabs and reposts from people who supported his right to voice his opinion.

"It's a shame that you are not allowed to say what you like," one person said in a comment on Gabbana's Instagram. "You have every right to say what you want, especially as you weren't disrespectful nor immature like Elton was. His comments are unnecessary, cheap and childish."

Gabbana issued a statement saying he and Dolce had not intended to judge others.

"We firmly believe in democracy and the fundamental principle of freedom of expression that upholds it. We talked about our way of seeing reality, but it was never our intention to judge other people's choices," the statement read.

Dolce also defended his views in statement and said he was not applying them to other people.

"I'm Sicilian and I grew up in a traditional family, made up of a mother, a father and children. I am very well aware of the fact that there are other types of families and they are as legitimate as the one I've known. But in my personal experience, family had a different configuration....I was talking about my personal view, without judging other people's choices and decisions," the statement read.