The five-page code of conduct, which has been under negotiation since 2005, was unveiled at a Geneva news conference by the World Council of Churches (WCC), a senior Roman Catholic prelate and the World Evangelical Alliance (WEA).
It urges Christians wanting "to share the good news of God's kingdom" -- missionary work or simply publicly testifying to their faith -- "to build relations of respect and trust with all religions" and adapt their approaches to local conditions.
It reaffirms their right to proselytize, or promote their beliefs and seek converts.
But it also urges them to abandon "inappropriate methods of exercising mission by resorting to deception and coercive means," saying that such behavior "betray the gospel and may cause suffering to others."
The code, entitled "Christian Witness in a Multi-Religious World: Recommendations for Conduct," comes amid growing tension between small local Christian communities and majorities from other religions in many, especially Muslim, countries.
This is often sparked by the activity of missionaries, both overt and covert, who seek to convert non-Christians, and are often denounced by local religious leaders -- Muslim, Hindu or Buddhist -- as enemies of what they see as the true faith.
In some Islamic countries, a Muslim who converts to another faith can face the death penalty, and Christians who proclaim their religion are often accused of blasphemy, which can also be a capital offence.
In recent years, there have been increasing incidents of attacks on Christian churches seen as the focus for conversion activity -- in Pakistan, Egypt, India, Indonesia and others -- in which many Christian believers have died.
The new code -- initially promoted by the Geneva-based WCC, which unites a wide range of Protestant and Orthodox churches -- says conversion "is the work of the Holy Spirit."
But Christians should "conduct themselves with integrity, charity, compassion and humility, and overcome all arrogance, condescension and disparagement" with regard other religions.
However, it declared that religious freedom -- which many activists argue does not exist in Muslim countries -- and the "right to publicly profess, practice, propagate and change one's religion" are based in human dignity.
And it calls on governments "to ensure that freedom of religion is properly and comprehensively respected, recognizing that in many countries religious institutions and persons are inhibited from exercising their mission."