The Lolita star made the strange comments in an interview with the Huffington Post in which he claimed a law allowing same-sex couples to officially marry could create a loophole to bypass the UK's heavy death duties.
He told the publication: "Could a father not marry his son?... It's not incest between men (because) incest (law) is there to protect us from inbreeding, but men don't breed..." adding, 'I don't have a strong feeling either way. Living with another animal, whether it be a husband or a dog, is great. It's lovely to have someone to love."
However, Irons' comments have angered some gay rights campaigners.
A spokesman for the Stonewall organisation has branded the actor's remarks "bizarre" and referenced his role as a corrupt pope in TV show The Borgias, saying: "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."
Openly gay Scottish actor Alan Cumming, who entered into a civil partnership with his husband in London in 2007 and then remarried him in New York last year, also took aim at Irons over the comments, writing in a post on Twitter: "I hate when people say they don't have strong feelings about something then proceed to spew offensive and ignorant ones. Jeremy Irons."