Three new doubly ordered perovskites NaYMWO6 (M=Mn, Co & Ni) have been synthesized by high pressure and high temperature. Analysis of room temperature laboratory X-ray diffraction data of these compounds suggests possible polar (P21) structure. However, the low scattering factor of oxygen does not allow us to determine the crystal structure unambiguously. Therefore, we require neutron diffraction to locate the oxygen position accurately and hence the crystal structure. The interesting aspect of these materials is that they exhibit dielectric anomaly and electric polarization at the antiferromagnetic ordering temperature (TN = 8 - 22 K). The objectives of this proposal are to determine the crystal structure in the paramagnetic state and magnetic structures of these compounds to understand the origin of electric polarization and mechanism of magnetoelectric effect.