Chief Rabbi Ephraim Mirvis is backing the Kavanah College bid for a new Jewish secondary free school.
A spokesman said Rabbi Mirvis was supporting the Kavanah proposal - which resulted from the Kedem High and Hertfordshire Jewish Free School (HJFS) bidders joining forces.
Kavanah's proponents had indicated that they wanted to operate under the Chief Rabbi's aegis and "constructive conversations" had been held.
The backers of another potential Jewish secondary free school, Barkai College, have said they will also make their application to the Department for Education before the September 28 deadline. Barkai's ethos is described as "modern Orthodox".
According to his spokesperson, Rabbi Mirvis's view was "it would be both irresponsible and impracticable to try to open more than one new school. As such, he will continue to encourage greater collaboration, in the hope that over the coming months, the Jewish community will be served by one application with broad appeal."
At an open meeting on Tuesday evening, Maurice Ashkenazi-Bakes of HJFS said he hoped for an answer from the DfE by February. Three potential sites had been viewed to serve pupils from Harrow, Hertfordshire and Brent.
