Its decision, announced by church leader Archbishop Christodoulos, placed the country's official religion on a collision course with a Socialist government that wants to bring Greece closer to the European Union and protect people's right to privacy.
An attack Friday by vandals against Greece's largest Jewish cemetery also has human rights groups and minorities worried that religious zealots may create problems. Unknown vandals painted Nazi slogans on the Athens cemetery's holocaust memorial, synagogue and more than 90 graves.
Premier Costas Simitis earlier this week announced full adherence to a 1997 law dropping the religion category from state-issued ID cards that all Greeks are required to have from age 14. He also turned down a church proposal to make the religion entry optional.
Christodoulos said the government's decision was part of a concerted effort by ``domestic and foreign'' forces seeking to weaken the church and wipe out the national identity of Greece.
The church has long considered itself as the guardian of the nation's soul, and its leaders fear the ID cards are a first step toward a formal separation of the church and state.
``The identity cards are just the tip of the spear aiming at the religious whitewash of our cultural and national life,'' Christodoulos said after a five-hour extraordinary meeting of the Holy Synod running the church.
Christodoulos demanded a referendum and said the church will use ``all legal means'' to make a religion entry optional on ID cards. They include appealing the legality of the 1997 law to the country's supreme administrative court.
The legislation had remained inactive because the government, apparently seeking to avoid a clash with the church, failed to issue a series of decrees putting the law into effect. Simitis said all necessary paperwork will now be carried out.
"The struggle will be relentless, with the force of the word," Christodoulos said, adding the church will not accept "any marginal behavior, fanaticism and hate which could be stirred up by those seeking to slander Orthodoxy."
The government has ruled out the possibility of a referendum, and government spokesman Dimitris Reppas said it would not budge on the ID issue.
"It is also positive that the church condemns any demonstrations of fanaticism," Reppas said.
But the cemetery desecration has some people worried the church will not be able to control religious zealots.
"The attack occurred two days after the announcement of the government for the deletion of religion from the new identity cards, which stirred strong protests from the church, ultra-orthodox organizations and far right groups," the Central Board of the Jewish Communities of Greece said.
More than 90 percent of Greece's 80,000-strong Jewish community was wiped out by the Nazis, and they have repeatedly expressed concerns they could be targeted by fringe groups.
"In some far right circles it was written that the Jews were responsible for the ID card issue," said Jewish Community president Moses Constantini.
Simitis' decision to abolish the religion entry has been backed by human rights groups and minorities such as Muslims, Jews and Roman Catholics, who claim the religion entry breeds exclusionary nationalism and allows for discrimination.
In many ways, the ID feud encapsulates Greece's growing pains. With a maturing economy and less parochial political outlook, Greece is finally being embraced as an equal partner by Western Europe. It is expected to receive approval to join the EU's single currency group in June.
A forward-looking perspective worries the church, which has cast heavy influence over Greek affairs for centuries. Christodoulos and other clerics attack any suggestions that they should limit their roles to purely spiritual matters.