Andy Burnham, leading candidate for the Labour leadership, has defended his record on gay rights and described how he sacrificed relationships within both family and church as he maintained his support for LGBT equality.

Speaking to Pink News, he attacked criticism of his record on the issue as hurtful and unfair. Burnham, who was the first Labour front-bencher to advocate openly for gay marriage, spoke of his struggle with the Catholic Church and with faith in general.

He admitted that Labour had in the past taken for granted a large vote from the LGBT community, but at the last election PinkNews polling showed the Conservatives ahead for the first time, after Cameron pushed ahead on gay marriage, something Gordon Brown refused to do. "How do you win back those people? We lost a lot of communities who would have traditionally affiliated towards us. We lost Labour-leaning business people, the Asian community, the Jewish community, and then LGBT people as well."

Key to all this was losing touch with millions of people over the economy. "There was a failure to explain our record in the government on the economy, we let the Tories define our record and claim that everything was to do with Labour's mess. Our failure to counter than put us in a weak position when it got to the election." While people were worried about the health service under Cameron, they still did not trust Labour on the economy.

He was speaking after a piece in the New Statesman questioned his LGBT voting record, in particular when in 2008, he voted for an amendment tabled by the leading Conservative politician Iain Duncan Smith saying there was a need for a father in IVF care.

Burnham said: "I found the piece quite hurtful, actually. If you look back over my fourteen years in Parliament, I've voted for everything [on LGBT rights] – I was absent for a vote in 2002 because my daughter was born. It was the day before or the day after. I was on paternity leave – so I've voted for everything.

"The reason why I say it's quite hurtful is because that has put me at odds, I have been repeatedly at odds with the Catholic church for all of my time as an MP. I have always been going against what they were saying, and that is challenging.

"That creates a personal challenge – I've been at odds with my own family, and that has been to some personal cost at times in terms of relationships with people. I don't say this to elicit any sympathy but a relative of mine died last night who was a councillor on Liverpool city council for many years, and he and I were very close, but the one time we fell out massively was over same-sex marriage, and it was a real fall-out.

"The reason I mention that is I have caused myself to change my own relationships, not just with the church but with members of my own family, in this cause... and then you get things written like that and it feels deeply unfair and hurtful."

On the IVF question he said he now felt the law had it right because children are entitled to know who their biological father is. He said: "Just to explain – I felt that there is an equality issue at stake in that in any context when you're thinking about IVF you have to think about the balance of parents with children. You have to think about what are the children's rights. The issue that I had a concern about is actually now dealt with in law – under any form of IVF, any child can actually trace their biological father, so that is completely dealt with."

Burnham said once that he was devoted to Everton, the Labour party and the Catholic Church, which is a fantastic quote.

But he now rarely goes to Mass.

He explained: "Though I did say that, and the Church did have a part in my upbringing, I am not a regular church-goer, I have to admit – even if that might cause me difficulty at home, in terms of my kids' schools."

He also said recently he hoped the Pope would come out for LGBT rights, although he admitted to Pink News this was unrealistic.

He added, referring to the Irish vote for gay marriage: "It needs to be said though doesn't it? I think they're getting themselves into a really dangerous position. I think it's a big moment for the Church, when Ireland of all places votes in that way, for the Church to be massively at odds with public opinion in one of its most loyal heartlands. It's becoming a real issue- how can they possibly ignore it?"

He said he believes Pope Francis is innately sympathetic. "The question is – is he prepared to take on the Vatican hierarchy?"

He also said the so-called gay cure therapies should be "absolutely, unequivocally" banned.