We study the possibility of right-handed neutrino dark matter (DM) in gauged U(1)B−L×Z2 extension of the standard model augmented by an additional scalar doublet, being odd under the Z2 symmetry, to give rise the scotogenic scenario of radiative neutrino masses. Due to lepton portal interactions, the right-handed neutrino DM can have additional co-annihilation channels apart from the usual annihilations through ZB−L which give rise to much more allowed mass of DM from relic abundance criteria, even away from the resonance region like MDM≈MZB−L/2. This enlarged parameter space is found to be consistent with neutrino mass constraints while being sensitive to direct detection experiments of DM as well as rare decay experiments looking for charged lepton flavour violating decays like μ→eγ. Due to the possibility of the Z2 odd scalar doublet being the next to lightest stable particle that can be sufficiently produced in colliders by virtue of its gauge interactions, one can have interesting signatures like displaced vertex or disappearing charged tracks provided that the mass splitting δM between DM and the next to lightest stable particle (NLSP) is small. In particular, if δM<mτ=1.77 GeV, then we get large displaced vertex signature of NLSP while being consistent with neutrino mass, lepton flavour violation and observed relic density. © 2019 The Authors