Tim Farron has refused to say whether he believes homosexuality is a sin after a caller repeatedly pressed him on the issue during a radio interview.

The Liberal Democrat leader was asked about his views on gay relationships during an appearance on LBC on Friday morning. Farron, a practising Christian, has been repeatedly questioned on the topic due to an evasive answer he gave on homosexuality two years ago. Last month, he said he did not believe being gay was a sin and that he was proud of his party’s record on LGBT rights.

The caller, Brian from Highgate in London, said: “You talk about people who pervert the religion of Islam for their own ends. I think you’re actually perverting the religion of Christianity … It doesn’t seem at all liberal, your attitude, and I’d like to know why you feel like this.”

Farron repeated that he had been a constant campaigner for LGBT rights. “I joined the Liberals when I was 16 and amongst the things I did in my first couple of years as a Liberal was to be on the frontline of the protest against Section 28, which was introduced by the Conservative government, which was banning the promotion of homosexuality,” he said.

The caller responded: “You think that homosexuality is a sin. I think that’s a perversion of Christianity – that’s the question I want you to address. I’m not asking you about that; what I want to do is find out more about you as a human being, as a person, and your religion is a very important part of you as a person while you are standing for this election. I want to know why you think homosexuality is a sin.”

“I am a political leader and I am a liberal to my fingertips,” Farron said, at which point host Nick Ferrari told him to answer the question.

“I dealt with that weeks ago,” Farron said. “You know what, we’re not going there. My personal faith is my personal faith.”

Asked again, he added: “Brian, you heard me talking about it weeks ago. Because to be honest with you, a person who is the leader of a political party, it’s their job and [as] someone who’s passionate about LGBT+ rights, prove it by your actions not by your words.

“And my actions absolutely are 100% are about defending LGBT+ rights and as a party, you look at what we’ve done. Lynne Featherstone, my colleague in government, she introduced equal marriage. I am proud of what she’s done.”

When asked a final time, Farron insisted: “I’ve already answered that, let’s move on.”

Absolutely and utterly UNBELIEVABLE that @timfarron refuses to say that homosexuality is not a sin AGAIN @LBC wow wow wow he was doing well — Luke Jerdy (@LukeJerdy) June 2, 2017

Why is Tim Farron refusing to say that he doesn't think homosexuality is a sin? Again! #LBC — Sebastian Mann (@sebmann1) June 2, 2017

Farron has said the question of homosexuality and sin was something he gets asked because of his faith. The question first arose two years ago during an interview on Channel 4 News, to which he had responded: “We are all sinners.”

The remark was raised again in an interview last month, and in the Commons where, asked again whether he believed being gay was a sin, Farron replied: “No, I do not.”