The nationwide campaign to collect signatures, which the church has dubbed an ``informal referendum,'' marks the first time in its 150-year history that the Greek church has so openly challenged the authority of a government to legislate.
``The Holy Synod, in accordance with the expectations of its faithful children and to fulfill its promises for the most broad popular expression, has decided to hold an informal referendum of religious conscience,'' said church spokesman Metropolitan Kallinikos.
Premier Costas Simitis' Socialist government said the church's decision could endanger the unity of the Greek people. He has said the entry runs counter to Greece's efforts to become a modern European country and violates 1997 privacy protection legislation.
A spokesman said the government will not repeal its decision to abolish a religion entry on the ID cards all Greeks are required to carry.
``Everyone takes responsibility for their actions, much more in view of procedures that could result in the division of Greek society,'' government spokesman Dimitris Reppas said.
He called on the church to respect the constitutional separation of authority and reminded clerics that religious groups were not supposed to meddle in politics.
Politicians, academics and critics say the church crusade has essentially transformed the religious group headed by Archbishop Christodoulos into a political party.
Christodoulos has also angered politicians and academics by saying that those opposed to includin greligion on ID cards ``belong to the forces of evil.''
``It is an open challenge to our democratic system,'' said Dimitris Papadimoulis, a deputy with the left coalition party.
According to a decision by the Holy Synod, the church's ruling body, the petition drive will begin this fall and will be restricted to ``responsible adults.''
The church claims it can collect nearly 5 million signatures in this country with a population of 10.5 million. Greece has an aging population, and according to the National Statistical Service there are 8.28 million men and women in the country over age 15.
Some of Christodoulos' senior clerics have expressed the hope that the government will collapse because of the campaign and a series of mass rallies.
A report issued Tuesday by the European Commission on Racism and Intolerance called on Greece to remove the religion entry ``in order to limit covert discrimination against members of non-Orthodox religions, who may in some cases be considered less Greek.''
Many church leaders are deeply suspicious of the modernization drive. They see it as a threat to the Christian Orthodox character of the nation and possibly the stirrings of an eventual separation of church and state in Greece.
About 97 percent of Greece's native-born population is baptized into the Orthodox Church, which sees itself as the true guardian of Greek identity and traditions.
Orthodox leaders have traditionally enjoyed deep respect as keepers of an essential element of the Greek ethnic identity during four centuries of Muslim Ottoman rule. The church helped fan the 1821 independence revolt and itself became independent from the Ecumenical Patriarchate in Istanbul, Turkey, in 1850.
Christodoulos has repeatedly said Greece owes its independence to the church.