  A left-right model of quarks and leptons based on the gauge group $SU(3)_c
\times SU(2)_L \times SU(2)_R \times U(1)_{B-L}$ is studied. Here the scalar
sector consists of only two doublets namely (1,2,1,1) and (1,1,2,1) but
familiar bidoublet (1,2,2,0) is removed. Quarks and charged leptons get mass
from a single see-saw mechanism but neutrinos get mass from a double see-saw
mechanism. In this type of models the heaviest right handed neutrino can be of
order $10^{13}$ GeVs or less in a natural way, depending on the size of related
Yukawa couplings.
