Sephardi members have hit back at their leaders over their disputed election of Rabbi David Bassous as the community's next spiritual head.

Alan Bekhor, who is leading a group of 20 concerned members of the Spanish and Portuguese Jews' Congregation, said that the resolution passed last week by its board of elders insinuated that Rabbi Bassous had been fairly elected.

Mr Bekhor said that his lawyers from Simmons and Simmons, who are advising his group, take the view that Rabbi Bassous had polled too few votes to secure a mandate.

His group have accused the elders of failing to acknowledge problems with the election: one dissident, Jonathan Sacerdoti, said that the leaders were "digging their heels in."

London-born Rabbi Bassous, who heads a Sephardi congregation in the USA, polled 268 votes in favour to 134 against in a ballot of members of the Spanish and Portuguese Jews' Congregation three weeks ago – exactly the two-thirds majority needed to take office under its constitution.

But those who oppose the choice of Rabbi Bassous say that one of two ballot papers classed as spoiled or doubtful in fact indicates a no-vote, which if counted would deprive him of his necessary majority.

In a resolution passed on Wednesday, the elders expressed "dismay" at "the arguments being put forward by a minority of the kahal [congregation] to derail the appointment" and expressed concern that dissenters would "take matters into their own hands in a more radical way, as has already been intimated to us".

Mr Bekhor said that he was in negotiations with Alan Mendoza from the mahamad (executive) and the congregation's current spiritual head Rabbi Abraham Levy.

In a statement, the concerned members group said that Rabbi Bassous "has not been elected. Quite simply, because he failed to convince a sufficient number of open-minded members that he was the right man for the job. He failed to win the election: we must move on."

But the mahamad responded on Friday with a statement to members of the congregation, declaring: "We would like to clarify one particular point: Rabbi Bassous won the election. The ‘concerned members’ appear to want to intimidate the Mahamad and Elders into denying this. We will not yield to their threats as we have received legal and halachic opinion that supports our position – and as a synagogue we must also take into account Jewish law as well as English. We hope that yehidim will support our position and not allow this group to decide our destiny based only on the fact that they are not willing to compromise. We still hope that we can build a shared future utilising their experience and viewpoints, but cannot accept that this gives them the right to dictate terms to you – the membership.”