Tim Farron, the new Liberal Democrat leader, refused to say whether he believed gay sex was a sin during a live television interview.
Farron was asked three times by Channel 4 News presenter Cathy Newman whether he personally believed, as a Christian, homosexual sex was a sin.
He repeatedly avoided answering the question.
Farron has been criticised in the past for abstaining on votes on same-sex marriage.
As he was pressed to answer the question, Farron replied: "To understand Christianity is to understand that we are all sinners."
He added: “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.’”