Outspoken former Conservative chairman Lord Tebbit has warned that gay marriage would lead the way for a lesbian queen giving birth to a future monarch by artificial insemination.
Tebbit also claimed that legislation would pave the way for him to be able to marry his son to avoid paying inheritance tax.
In an interview for the Big Issue, Tebbit said he believed the government had "f****d up" by not listening to Tory peers on gay marriage legislation.
David Cameron had not properly considered how it would affect how future kings or queens of England would be born, he continued.
The gay marriage bill, which caused open ruptures in the Conservative before and during Monday's vote, scraped through with Labour support.
But Tebbit said that Downing Street had tried to push the legislation too quickly and had not considered the full ramifications.
He said: "The government discussed it for 20 minutes on the morning of its announcement. They'd done no work on it beforehand.
"I said to a minister: have you thought this through? Because you're doing the law of succession, too.
"When we have a queen who is a lesbian and she marries another lady and then decides she would like to have a child and someone donates sperm and she gives birth to a child, is that child heir to the throne?'
"It's like one of my colleagues said: we've got to make these same-sex marriages available to all."
Tebbit also joked that the law would allow parents to marry their own children to avoid paying inheritance tax.
He added: "It would lift my worries about inheritance tax because maybe I'd be allowed to marry my son. Why not? Why shouldn't a mother marry her daughter? Why shouldn't two elderly sisters living together marry each other?"
Tebbit was recently involved in a scathing attack on fellow senior Conservative member Lord Howe, who he accused of "bleating" in favour of Brussels against Britain.
Discussing Ukip's recent rise, Tebbit added that Nigel Farage's party would make greater headway if it continued its success in the European elections.
He said: "I know there's people rich enough to get involved and fund a significant campaign at a general election."