The Charity Commission has identified several Christian and Jewish "closed or exclusive religious organisations" that it feels might not meet public benefit requirements, according to a letter seen by Third Sector.
The letter to the office of Dominic Grieve, the Attorney General, was written two years ago by Kenneth Dibble, head of legal services at the commission.
It asked that the Attorney General make a reference to the charity tribunal to consider the public benefit of religious groups "where the adherents have limited interaction with the wider public".
Dibble’s letter said it would be difficult to estimate the number of other groups that might not meet public benefit requirements, but said they might include the Plymouth Brethren Christian Church, as well as Amish, Bruderhof and Mennonite Christian groups, Hasidic and Messianic Jews and "possibly some Buddhist organisations".
"The commission considers that this matter does require consideration and an authoritative view as to the effect of the Charities Act 2006 following the removal of the presumption of public benefit for the charitable purpose of the advancement of religion and how the assessment of public benefit is to be determined in the context of closed or exclusive religious organisations," the letter said.
A reference would deal specifically with the Preston Down Trust, a congregation from the Plymouth Brethren Christian Church, the letter said.
The Attorney General did not make a reference, and his office replied suggesting that the commission might refuse charitable status to the trust, guidance published by the commission earlier this month showed.
The regulator has since done so, and the trust has appealed the decision to the charity tribunal.
Jonathan Benjamin, chief executive of the Board of Deputies of British Jews, a representative body for the Jewish community, said he was concerned that many synagogues would not meet the public benefit rules laid down by the Charity Commission.
"The commission has talked about closed groups," he said. "But synagogues don't normally publicise service times. You often wouldn't be able to walk in off the street - you'd have to be an invited guest. And we wouldn't proselytise.
"This suggests these rules could have a wider scope than the commission anticipates."
A spokeswoman for the commission said it had a policy of not commenting on leaked documents but issued a statement from William Shawcross, its chair, which said: "The issues concerning the Preston Down Trust, currently subject to an appeal before the tribunal, are specific to this particular organisation. I believe the tribunal will clarify the questions of law in this matter.
"The commission has not changed its approach to registering religious organisations, which we do according to charity law. I am well aware of the vital role that religious charities have played in British society for centuries."