POPE FRANCIS has defended gay people against discrimination and said they should be integrated into society, but reaffirmed Church teaching that homosexual acts are a sin.

The comments, in an 80-minute conversation with journalists on a plane bringing him back from a week-long visit to Brazil, are among the most compassionate words from any pontiff on gay people.

During his comments he added that the Church's ban on female priests was definitive, although he would like women to have more leadership roles in administration and pastoral activities.

Defending gay people from discrimination, Pope Francis said: "If a person is gay and seeks God and has good will, who am I to judge him?"

However, he pointed to Catholic teaching which ruled that, while homosexual orientation is not sinful, homosexual acts are.

He said: "The Catechism of the Catholic Church explains this very well. It says they should not be marginalised because of this (orientation) but that they must be integrated into society.

"The problem is not having this orientation. We must be brothers. The problem is lobbying by this orientation, or lobbies of greedy people, political lobbies, Masonic lobbies, so many lobbies. This is the worse problem."

Francis was answering a ­question about reports of a gay lobby in the Vatican.

He joked: "You see a lot written about the gay lobby. I still have not seen anyone in the Vatican with an identity card saying they are gay."

Addressing the issue of women priests in the first time he has spoken on the subject, the pope said: "We cannot limit the role of women in the Church to altar girls or the president of a charity, there must be more.

"But with regards to the ­ordination of women, the Church has spoken and says no. Pope John Paul said so with a formula that was definitive. That door is closed," he said, referring to a document by the late pontiff which said the ban was part of the infallible teaching of the Church.

The Church teaches that it cannot ordain women because Jesus willingly chose only men as his apostles. Advocates of a female priesthood say he was acting according to the customs of his times.

Many in the Church, even those who oppose a female priesthood, say women should be given leadership roles in the Church and the Vatican administration.

Pope Francis also said the ­troubled Vatican bank must become honest and transparent and that he will listen to the advice of a commission he has set up on whether it can be reformed or needs to be shut down altogether.

He said: "I don't know what will become of the bank. Some say it is better as a bank, others that it should be a charitable fund and others say close it."

The bank, formally known as the Institute for Works of Religion (IOR), is the target of several investigations by Italian magistrates on suspicion of money laundering.

Francis said: "Whatever the ­solution, it must have transparency and honesty. That's the way it must be."

Francis arrived back in Rome yesterday after a triumphant week-long tour of Brazil.

It ended with a huge gathering on Rio de Janeiro's famed Copacabana beach for a world Catholic youth festival which organisers estimated to have attracted more than three million people.