A low-pressure mercury vapor discharge lamp comprises a discharge vessel (10) having a tubular portion (11). The discharge vessel (10) encloses a discharge space (13) provided with a filling of mercury and a rare gas in a gastight manner. The tubular portion (13) of the discharge vessel (10) is provided with a metal oxide layer (15) and a luminescent layer (17) on a surface (14) facing the discharge space (13). The discharge lamp comprises means for maintaining an electric discharge in the discharge vessel (20b). The discharge lamp is characterized in that the luminescent layer (17) comprises an alkali metal oxide. This alkali metal oxide is preferably sodium oxide and/or potassium oxide, and the concentration of the alkali metal oxide is 0.002.ltoreq.Na.sub.2 O.ltoreq.0.1% by weight and/or 0.002.ltoreq.K.sub.2 O .ltoreq.0.1% by weight. The tubular portion (11) of the discharge vessel (10) preferably has a further metal oxide layer which acts as an alkali metal-repellent layer. This further metal oxide layer preferably comprises silicon oxide. The lamp according to the invention has a comparatively low mercury consumption.