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".
