A series of mercury based cuprates with nominal composition Hg 1 - y V( y )Ba 2 - x Sr x CuO 4 + 2 y + δ has been prepared for x = 0, 0.25, 0.5, 0.75, 1 and 1.25. The actual solid solution limit from the EDS measurement is x = 1.1, y ranges from 0.2 to 0.35. The single crystal study coupled with high resolution electron microscopy shows for the first time the presence of VO 4 tetrahedra replacing partly the mercury atoms according to the formulation Hg 1 - y (VO 4 ) y (Ba,Sr) 2 CuO 4 - 2 y + δ . The role of vanadium for the stabilisation of the structure and as a doping agent in the superconducting properties is discussed.