Between 50 and 100 gay-rights protesters, shouting "Pell go to hell!", greeted the controversial footy-loving priest from Ballarat when he arrived for the ceremony in a black limousine.

Ugly scenes broke out between police and protesters as Dr Pell met Aboriginal elders and climbed the steps of St Mary's Cathedral to greet the assembled 350 priests and 45 bishops.

A woman was arrested and dragged away after allegedly kicking a male police officer in the groin. Two other protesters were taken away for breach of the peace.

The protesters, whose chants clashed with the Catholic singing groups, were angry that Dr Pell continues to exclude them from his church. "Pell says homosexuality is worse than smoking," said Edwina Kay, 18. "The Catholics have put enormous pressure on young gay people and their rates of suicide are much higher than other young people."

Inspector Ron Mason defended the actions of police against protesters. "We will put up with a lot, but not that (policemen being kicked in the groin)," he said.

In his address to the 3000-strong congregation, Dr Pell defended his views on sexuality. "Christian teaching on sexuality is only one part of the Ten Commandments, of the virtues and vices, but it is essential for human wellbeing and especially for the proper flourishing of marriages and families, for the continuity of the human race."

The former Archbishop of Melbourne said that Sydney may be called "sin city", but human weakness, which flourished all over Australia, was not a recent Sydney invention.

The church must attract more young men to the Catholic priesthood, Dr Pell said. Its central challenge, however, was to reverse the decline of religion in Australia. "The most significant religious change in Australia over the last 50 years is the increase of people without religion, now about one-fifth of the population, more among young people," Dr Pell said.

"All monotheists, Christians and Jews, Muslims and Sikhs, must labor to reverse this."

He also said that the church must face the challenge of reconciling with indigenous populations.