, he said: "I'm allowed to say what I think and people are absolutely entitled to say back what they think.
"I believe in free speech - and protecting it - is very important.
"Rape is a great evil and a terrible crime, but that's not made better by then aborting the unborn child.
"The Catholic Church's teachings are authoritative. To take a life after a rape is not the answer.
"Life begins at the point of conception. One can only feel compassion for a woman in these situations - which, of course are rare - but it's hard to see how taking a child's life makes them better."
Former Labour deputy leader Harriet Harman today branded him a "deadbeat dad" but he hit back saying he would "lose little sleep" over her criticisms.
He was asked by GMB presenter Susanna Reid earlier in the week: "Are you completely opposed to abortion in all circumstances?"
And he replied: "Yes I am."
He was pressed further by the pair - who asked whether that would apply even in case of rape and incest.
Mr Rees Mogg said: "I’m afraid so. Life is sacrosanct and begins at the point of conception. I think it is wrong."
But Piers Morgan his back and quizzed: "Say you were Prime Minister, and a woman is raped by a family member, you would say she has absolutely no right to have that baby aborted?"
But Mr Mogg insisted that "she would have a right, under UK law. The law is not going to change.
"My personal opinion that abortion is morally indefensible."
And on gay marriage he said: "Marriage is a sacrament that lies with the church. I support the teaching of the Catholic church."
The MP has repeatedly voted against sex marriage legislation.
He tweeted later this afternoon a message in defence of his deeply held views, and that they are those held by the Christian Church.
He said: "Et unam, sanctam, catholicam et apostolicam Ecclesiam" which is Latin for "one, holy, catholic and apostolic church". The words can be traced back to 381 as an antidote to herasies that crept into the church.
The rising star, who yesterday was tipped to be the next leader of the party by a members poll, said that "people are entitled to hold these views".
And even if he didn't agree with others' lifestyles, he said it was "not for me to judge what other people do".
He also stepped up to defend ex Lib Dem leader Tim Farron, who stepped down after the election saying his faith was not compatible with being a political leader.
But Mr Rees Mogg was slammed by political opponents who branded his comments “from the dark ages.”
Labour’s Stella Creasy said “the jokes not funny anymore.”
However the PM stood by the the Somerset MPr, saying his faith was a personal matter.
No10 said Theresa May disagreed with Jacob Rees Mogg but it was a matter “conscience.”
After a controversial discussion on yesterday's show, the MP said that it was far more effective to battle over ideas and opinions than to refuse to air them.
He said that restricting free speech was "dangerous to democracy".
The Somerset MP, who has shot to online fame in recent months, batted away speculation that he would challenge Theresa May for the leadership of the party, insisting he was completely loyal to her.
Last night he said he was more likely to become POPE than PM.
Mr Rees Mogg said: "There is not a leadership election in the Tory party, and if there were, I would not be a candidate.
"The party candidate has never gone from a backbench MP to be prime minister."
The Brexiteer insisted that the PM's position is "stronger than suggested" and politics changes very quickly.
"When the election was called, people thought this was going to be the curtain call for Jeremy Corbyn," he added.
"A few months later, he is top of the pops, the strongest leader in the country."
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