Also denied marriage rights in Israel are: 13,000 Jews whose conversions overseas are rejected by the Rabbinate; 80,000 male cohenim, descendants of a Jewish priestly caste who are not allowed to marry converts or divorcees; and 284,000 LGBT people.
There are a further 5,000 Israelis classified as equivalent to "untouchables." Last year it emerged that the rabbinical courts kept a "blacklist" of women they would not allow to marry, or remarry following a divorce, based on an assessment of their sexual history.
The rabbis have additional control over other rights related to marriage, such as custody. In a high-profile case in 2014, a mother was denied contact with her children after she started a lesbian relationship. The rabbis ruled that contact would cause the children "irreversible psychological harm."
In both cases the secular high court refused to intervene, apparently fearful of provoking a rift with Israel's religious public.
According to Hiddush's figures, an additional 400,000 Israelis may face restrictions on marriage, even though they are not banned outright.
Cornfeld said the rabbinate carried out intrusive checks on couples' personal and family histories to prove their Jewishness. Those could include investigations into whether a maternal grandmother spoke Yiddish or was buried in a Jewish cemetery.
Couples might also be required to provide testimony from rabbis overseas confirming their Jewishness.
"For some couples who are Jewish [according to halacha] those checks can take months or years and many are not prepared to endure the delays and the humiliation," said Cornfeld.
Faced with these obstacles, he added, many couples preferred either to marry abroad or to cohabit. "The new trend is towards cohabitation," he said. "If you don't want the Chief Rabbinate in your lives, it is the only way."
Farber, of Itim, told MEE the religious authorities had stonewalled his efforts to make their procedures more transparent.
On six occasions over the past two years, he said, the rabbinate had failed to respond to his requests for a list of the overseas rabbis whose testimonies are accepted in determining whether an immigrant is Jewish.
Without such testimony, immigrants cannot marry or be buried in a Jewish cemetery.
This month, the Israeli Supreme Court ordered the rabbinate to produce such a list within the next month. Judge Nava Ben-Or said she was "shocked" by the rabbinate's behavior. "I am ashamed that in a functioning state this information cannot be provided. It is an unprecedented scandal," she said.
Daniel Bar, a spokesman for the Chief Rabbinate, told MEE the criticisms were unwarranted. "Marriage is a religious matter -- that is the law in Israel. There is nothing more to say about it."
Public oppositionMichal Reshef, a lawyer, married in an unrecognized ceremony organized by Havaya last month. She and her American husband, Benjamin, were denied a recognized wedding in Israel because he is not Jewish.
The couple's marital status will only be recognized in the spring when they return from a second wedding in the US.
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