John, 67, stirred up a social media storm on Sunday when he called for a boycott of the designer label in reaction to comments in which Domenico Dolce referred to babies conceived through IVF as "synthetic".
In comments endorsed on social media by celebrities including Victoria Beckham, Ricky Martin, Courtney Love and Martina Navratilova, the gay star accused the Italian duo of "wagging your judgemental little fingers at IVF."
In a typically scathing post on Instagram, he added: "Your archaic thinking is out of step with the times, just like your fashions. I shall never wear Dolce and Gabbana ever again. #BoycottDolceGabbana."
The designers, who are also gay and were in a long-term relationship with each other until a few years ago, said it was the veteran British rocker who was being judgemental.
Dolce said his comment that IVF was not for him should not have been interpreted as disapproval of anyone else's choices.
"I'm Sicilian and I grew up in a traditional family, made up of a mother, a father and children," he said in a statement.
"This is the reality in which I grew up, but it does not imply that I don't understand different ones. I was talking about my personal view, without judging other people's choices and decisions."
His business partner Gabbana revealed that he had been so infuriated by John's statement that he had posted the comments #fascist and #boycotteltonjohn on the Instagram page.
'This is ignorance'
Speaking to Italian daily Corriere della Sera's web edition, Gabbana said he had expected better from a singer he once admired.
"I didn't expect this, coming from someone whom I considered, and I stress 'considered', an intelligent person like Elton John.
"I mean, you preach understanding, tolerance and then you attack others?
"Only because someone has a different opinion? Is this a democratic or enlightened way of thinking? This is ignorance, because he ignores the fact that others might have a different opinion and that theirs is as worthy of respect as his."
He said he had not tried to contact the pop star.
"That would be useless! It's an authoritiarian way of seeing the world: agree with me or, if you don't, I'll attack you."
Gabbana added: "Domenico has his ideas, he made some choices. Elton John made different choices. Different choices, different lives. Equal respect.
What I see, particularly online, is a lot of gay people who are homophobic: gay people who will attack other gay people who express ideas that are different from theirs."
John has two young sons with his husband David Furnish who were conceived through IVF and born thanks to a surrogacy arrangement.
In the interview which caused the storm, Gabbana said he would have a child tomorrow if he could, while Dolce explained why he did not feel he could go down that road.
"You are born and you have a father and a mother," he told Panorama magazine.
"Or at least that's the way it should be, and that's why I'm not convinced by children from chemistry, synthetic babies, uteruses for rent, semen chosen from a catalogue."
Beckham weighed into the row on Monday by tweeting: "Sending love to Elton David Zachary Elijah & all the beautiful IVF babies."
Gay Latino star Ricky Martin, who has five-year-old twins, on Sunday accused the Italian duo of fuelling bigotry.
"@dolcegabbana ur voices R 2powerful 2B spreading so much h8," he tweeted. "Wake up,Its 2015 Luv urselves guys #boycottdolcegabbana."
Privately, D&G executives admit that the celebrity backlash could do some temporary damage to the company's global brand and sales but predicted that the "storm in a test tube" would blow over in a week or so.