An ink supply arrangement for an inkjet printhead, the inkjet printhead having a plurality of ink ejection nozzles, the ink supply arrangement comprising: at least one ink bag containing ink for distribution to the nozzles via a fluid path between the ink bag and the nozzles, the ink being primed in the fluid path and nozzles so as to be ejected by the nozzles, in use, thereby depleting the ink contained in the ink bag, the ink bag being configured to collapse as the ink is depleted; a body for housing the ink bag and the printhead, the ink bag being attached to the body at a wall opposite a wall of the ink bag facing the printhead; and a biasing member arranged in the ink bag to apply outwardly directed force on at least the wall of the ink bag facing the printhead, wherein the biasing member is configured to maintain substantially constant negative pressure at the nozzles as the ink is depleted from the ink bag.