Luxury goods brand Dolce & Gabbana is in hot water after criticising gay adoption and in vitro fertilisation in a series of controversial statements last week.

Founders Domenico Dolce and Stefano Gabbana, who are openly gay, voiced opposition to many tenets of LGBT rights in an interview with Italy's Panorama Magazine.

"We oppose gay adoptions. The only family is the traditional one," the men said in a translation provided by LGBT News Italia. "No chemical offsprings and rented uterus: life has a natural flow, there are things that should not be changed."

"The family is not a fad," Gabbana said. "In it there is a supernatural sense of belonging."

Dolce added that procreation "must be an act of love," and criticised children created through artificial insemination.

"You are born to a mother and a father – or at least that's how it should be," he said. "I call children of chemistry, synthetic children. Uteri [for] rent, semen chosen from a catalog."

In 2013, Dolce confirmed to The Telegraph that he is a "practising Catholic" and opposed to gay marriage, and Gabbana voiced his opposition to gay marriage in a 2006 interview with the Daily Mail.

Despite the consistent messages from the designers, many remained unaware of their convictions until last week.

"How dare you refer to my beautiful children as 'synthetic,'" Sir Elton John wrote on Instagram.

"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."

Former tennis star and open lesbian Martina Navratilova, singers Ricky Martin and Courtney Love, and others have joined in the boycott against the iconic brand.

The designers initially reposted messages of support they received for freedom of speech and traditional families, but issued a statement on Sunday apologising for causing offense.

"It was never our intention to judge other people's choices," Gabbana said. "We do believe in freedom and love."

"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," Dolce added.