A gas discharge lamp for dielectrically impeded discharges, which gas discharge lamp is provided with a discharge vessel filled with a gas filling, which discharge vessel comprises at least a wall of a dielectric material and at least a wall having a surface which is at least partly transparent to visible radiation and coated with a phosphor layer, which phosphor layer comprises a phosphor preparation of a phosphor powder and a coating, which coating comprises a compound selected from the group formed by the fluorides and orthophosphates of the elements magnesium, calcium, barium, aluminum, scandium, yttrium and lanthanum, and provided with an electrode structure for a dielectrically impeded discharge, and with means for igniting and maintaining the dielectrically impeded discharge.