Tim Farron refused to give a specific right or wrong answer on the subject, saying that all people are sinners and that we should look at our own lives rather than pointing the finger at others.
He also said Christians and Liberals do not enforce their views on others, and that he was not the leader of a religious movement like the Archbishop of Canterbury is, and therefore should not be expected to make public moral judgements on various issues.
Channel 4's Cathy Newman asked for Mr Farron's views on homosexual relationships on three separate occasions.
The Lib Dem leader said: "Perhaps the Bible phrase that I use most - particularly with my kids, but actually on myself, is 'You don't pick out the speck of sawdust in your brother's eye when there is a plank in your own'."
"Fundamentally, my faith is based upon my belief that Jesus Christ is who he said he is.
"... every single person is a sinner, and every single person has the offer of redemption as well.
"For what it's worth, this is absolutely not the interview for me to be the Archbishop of Canterbury. I have become the leader of the Liberal Democrats, I have not become the leader of any particular religious movement."
