More than 45,000 people have now been baptised at Rick Warren's Saddleback Church in California.

Warren called the moment "historic", before Alberto Flores became the 45,000th person to be baptised by the church.

Flores was baptised along with his 13-year-old son, Andre.

"This weekend is a historic weekend for our church," Warren told his congregation last Sunday, "because somebody in this group is going to be the 45,000th baptism of Saddleback Church. And I'm going to take whoever that person is, out to lunch."

Almost 800 people were baptised across Saddleback's 16 campuses last weekend alone, taking the total to 45,743.

"Baptisms are an amazing moment in the life of the church," Warren said.

"They are a public sign of new life in the believer, of new beginnings for all those involved, and they encourage everyone watching to renew their own commitment to Christ.

"We are grateful that God has graciously allowed us to be a part of more than 45 thousand people taking this amazing step and we pray that we'll get to be a part of many many more in the coming months and years."

The news follows research that suggests the US church is in decline.

Studies undertaken earlier this year by University College London (UCL) and Duke University in the US showed a drop in the number of Americans who claim religious affiliations, attend church regularly and believe in God.

Furthermore, researchers found that younger people are increasingly irreligious: "this decline has been produced by the generational patterns underlying religious decline elsewhere in the West: each successive cohort is less religious than the preceding one. America is not an exception."

The study found 68 per cent of Americans aged 65 and over said they had no doubt God existed, compared to 45 per cent of young adults, aged 18-30.

Saddleback said it saw its own increasing number of baptisms as a source of encouragement amid these statistics.