Jeremy Irons has responded to the outrage over his claims that the legalisation of same-sex marriage could lead to fathers marrying their sons, maintaining that his concerns are “valid” but adding he is not anti-gay.

Irons, 64, made the comments to the Huffington Post’s TV channel earlier this week. “Could a father not marry his son?” Irons asked host Josh Zepps.

When reminded about laws preventing incest, Irons replied: “It’s not incest between men”, because “incest is there to protect us from inbreeding, but men don’t breed.”

He was slammed for the remarks by numerous commentators. On Friday he responded to the public outrage caused by his remarks in a letter on JeremyIrons.net, saying his comments represented “a mischievous argument, but nonetheless valid”.

He wrote:-

I am deeply concerned that from my on line discussion with the Huffington Post, it has been understood that I hold a position that is anti gay. This is as far from the truth of me as to say that I believe the earth is flat.

I was taking part in a short discussion around the practical meaning of Marriage, and how that institution might be altered by it becoming available to same-sex partners. Perhaps rather too flippantly I flew the kite of an example of the legal quagmire that might occur if same sex marriage entered the statute books, by raising the possibility of future marriage between same sex family members for tax reasons, (incest being illegal primarily in order to prevent inbreeding, and therefore an irrelevance in non reproductive relationships). Clearly this was a mischievous argument, but nonetheless valid.

I am clearly aware that many gay relationships are more long term, responsible and even healthier in their role of raising children, than their hetero equivalents, and that love often creates the desire to mark itself in a formal way, as Marriage would do. Clearly society should find a way of doing this.

I had hoped that even on such a subject as this, where passions run high, the internet was a forum where ideas could be freely discussed without descending into name-calling. I believe that is what it could be, but it depends on all of us behaving, even behind our aliases, in a humane, intelligent and open way.

Political satirist Stephen Colbert mocked the Oscar winning actor for his comments earlier this week , joking “what’s to stop a man from dressing up as a woman to get equal pay. I mean insurance wise, it’s a nightmare.”

Alan Cumming, 48, who entered into a civil partnership with his husband in London in 2007 and then married him in New York last year, also criticsed Irons for the comments, tweeting: “I hate when people say they don’t have strong feelings about something then proceed to spew offensive and ignorant ones. Jeremy Irons.”

Ruth Hunt from gay rights charity Stonewall branded the actor’s remarks “bizarre” and referenced his role as a corrupt Pope in TV show The Borgias. She said: “Few people will agree with Jeremy Irons’ bizarre ‘concerns’ about equal marriage. Sadly his comments do seem to indicate he’s taken his role as a Pope in The Borgias a little too seriously.”

However, Fox News contributor Erick Erickson took Irons’ side, asking: “Seriously. Why not incest… If love and commitment are the justification for marriage, why exempt this?”