Simon Benscher, deputy chairman of Liberal Judaism and a Woodford Liberal Synagogue member, is to take over as chairman of the movement.
He succeeds Lucian Hudson, who bows out after six years in charge and at a time of continuing expansion.
The movement's annual patrons' dinner at the House of Lords on Tuesday was told that two new communities were waiting in the wings to affiliate.
One is the Lancaster and Lakes group. The other is understood to be a currently independent community in Europe. Over the past few years, Liberal Judaism has added seven new groups around the country - in Gloucestershire, Brentwood, Wessex, Crouch End, Stevenage, Suffolk and York.
A second Progressive chaplain is also being recruited to serve both Reform and Liberal students on campus.
The new position is the first tangible outcome of the alliance between the two Progressive movements announced last year.
Rabbis Richard Jacobi (Woodford) and Alexandra Wright (Liberal Jewish Synagogue, St John's Wood) are to jointly chair the Rabbinic Conference of Liberal Judaism, succeeding Rabbi Charley Baginsky.