The rift over the leadership of Britain's mainstream Sephardi community deepened this week with the opposing sides accusing each other of intimidation.

The mahamad (executive) of the Spanish and Portuguese Jews' Congregation is locked in a war of words with a group of senior members over the disputed election of Rabbi David Bassous as its next spiritual head.

In a statement issued to congregants last Friday, the mahamad hit out at the "campaign to destabilise our community" and "baseless hostility" towards Rabbi Bassous.

But a group of 20 "concerned members" maintain that Rabbi Bassous was not properly elected.

In a ballot of S and P members a month ago, London-born Rabbi Bassous, who heads a Sephardi synagogue in New Jersey, won 268 votes, with 134 against - exactly the two-thirds majority necessary to secure the post.

But the concerned members' group say that one of two papers originally declared invalid clearly indicated a no vote, which would deprive Rabbi Bassous of his majority.

The mahamad declared: "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."

So far the mahamad has not published such opinions.

This week the concerned members released a copy of their own legal advice. It said: "Leading counsel has advised us that where, as here, a voter has marked the ballot paper in such a way as to show a clear intention as to how he or she wished to vote, it would be a breach of the contract between the yehidim [members], constituted by the ascamot [rules of the congregation], to reject the vote."

A briefing paper issued by three of the concerned members – former president of the S and P board of elders, Lucien Gubbay, Board of Deputies delegate Jonathan Sacerdoti and head of the S and P lectures committee Alan Bekhor – criticised the mahamad for "intimidation, denigration and false accusations against those holding opposed views".

They wrote: "No one wants to see this dispute end in court. But any member is entitled to ask the Charity Commission to conduct an inquiry into the ultra vires actions of the trustees if he/she feels the leadership is acting illegally."