Sephardi leaders held an emergency meeting on Wednesday night to try to find a way out of the continuing dispute over the choice of its next rabbinic head.

London-born Rabbi David Bassous appeared to have won approval to succeed Rabbi Abraham Levy as spiritual leader of the Spanish and Portuguese Jews' Congregation in an election held by its membership three weeks ago.

But opponents of the rabbi, who believe he is too religiously right-wing for Britain's oldest Jewish community, insist that he fell short of the necessary mandate by a single vote.

Adam Musikant, chairman of the mahamad (executive) which recommended Rabbi Bassous, said in advance of this week's meeting that the community was "in a state of flux. We have to find a way forward.

"The community has voted by some two-thirds to one-third to move forward with Rabbi Bassous. That is a pretty overwhelming mandate for change, I would have thought.

Spoiled ballot papers ruin the result of the poll

"We are looking to Rabbi Levy to exert his considerable experience and leadership to ensure that our members get the change they voted for."

But amid rumours that the mahamad was preparing to resign en masse, Mr Musikant acknowledged that this was one option being considered.

Rabbi Levy, who has led the community since 1980, is 72 and now works part-time; his current contract runs for another two and a half years.

The members' vote had gone 268 to 134 in favour of Rabbi Bassous - exactly the two-thirds necessary, under the congregation's rules, to secure the post.

But opponents say that subsequent inspection of two spoiled or doubtful ballot papers showed that at least one of them was intended as a no-vote, which would deprive Rabbi Bassous of the required majority.

"I am quite sure he did not win and he will not be coming," said one senior member of the congregation.

According to an American source, Rabbi Bassous, who leads a Sephardi congregation in New Jersey, recently emailed congregants to say: "There have been a lot of rumours that we will be leaving town. They are false, we will be here for a while."

As members of the four synagogues under the S and P umbrella awaited resolution of the impasse, one member, David Ereira, who chaired its building fund, warned: "The community will unquestionably be split – I believe there will be at least two breakaways.

"In the past five years, we have lost nearly 25 per cent of our members. If we lose another 25 per cent, there will be practically nothing left.

"I will be amazed if Bevis Marks [the country's oldest synagogue] is open in two years unless we have a dramatic change of leadership."

The congregation is no stranger to close elections. Controversy broke out in 1977 when a vote to approve the retirement of its then spiritual leader Haham Solomon Gaon was tied at 75 for and 75 against: it was only carried on the casting vote of the chairman of the mahamad.