By Philip Pullella

VATICAN CITY (Reuters) - Pope Benedict, closing a gathering of bishops who discussed how to win back lapsed and lukewarm Catholics, on Sunday said the Church had to develop new ways of reaching out to those who had drifted from the faith.

Benedict, 85, said a solemn Mass in St Peter's Basilica to close the three-week synod of some 260 bishops from around the world on the theme of the "New Evangelisation," or how to stem the haemorrhaging of the faithful.

The Church is suffering desertions from its practising flock in former strongholds in Europe, North America and Latin America due to sex abuse scandals, increasing secularism, rival faiths and open dissent against Church teachings on homosexuality and its ban on a female priesthood.

"Besides traditional and perennially valid pastoral methods, the Church seeks to adopt new ones, developing a new language, attuned to the different world cultures ...," he said.

He did not name any new methods but recently the 1.2 billion member Church has increasingly turned to the Internet and social media to spread its message.

One of the 58 proposals made by the bishops at the end of the gathering called for Catholic leaders to be better trained in the use of electronic communications.

In his homily, the pope said Church leaders had to work harder to turn around a situation "where the light of faith has grown dim and people have drifted away from God, no longer considering him relevant for their lives".

The synod's final message, issued on Friday, said the Roman Catholic faith in many advanced countries risked being "eclipsed" by an increasingly secularized and materialistic world.

The message, a synthesis of the topics discussed, said that while the gospel could not be "a product to be placed in the market of religions", the Church needed to find new ways of putting it "into practice in today's circumstances".

Friday's message took a dig at the United States and Canada, saying the countries of North America needed to "recognize the many expressions of the present culture in the countries of your world which are today far from the Gospel".

The pope will use the deliberations at the synod and the proposals to write his own document, known as a "apostolic exhortation" on the topic.

(Reporting By Philip Pullella; Editing by Rosalind Russell)